The field of candidates is large and campaign trips to early voting states including Iowa, New Hampshire and South Carolina have been frequent. There's also no sign of the campaign launches slowing down.
Here's a list of all the candidates in the race (in alphabetical order):
Sen. Michael BennetThe senior senator from Colorado announced his presidential bid during a May 2 appearance on CBS This Morning, just weeks after a successful prostate cancer operation.
Bennet said his ability to win over Republican constituents and colleagues, and his "broad" experience in the public and private sectors, distinguish him in a crowded Democratic field.
"I think this country faces two enormous challenges, among others," he said in the CBS interview. "One is a lack of economic mobility and opportunity for most Americans, and the other is the need to restore integrity to our government."
Bennet caught people's attention with a viral speech on the Senate floor during the government shutdown in January. He he tore into Sen. Ted Cruz, R-Texas, for the role he said he played during another government shutdown in 2013.
The former school superintendent is now the twenty-first Democratic candidate, the seventh senator and second Coloradoan -- after his colleague, former Gov. John Hickenlooper -- to enter the race.
Former Vice President Joe BidenThe former vice president and senator from Delaware became the 20th candidate in the Democratic field after announcing his bid April 25 in an online video.
In the video, he denounced the white supremacists who marched on Charlottesville in 2017 and President Donald Trump's response, calling it a "defining moment for this nation in the last few years."
"We are in a battle for the soul of this nation," Biden said in the video.
Biden's campaign website lays out the three pillars of his campaign: rebuilding the middle class, reclaiming American leadership on the world stage and fostering an inclusive democracy-notions that he said are at stake in the coming election.
"Folks, America is an idea. An idea that's stronger than any army, bigger than any ocean, more powerful than any dictator or tyrant. It gives hope to the most desperate people on earth, and guarantees that everyone is treated with dignity, and gives hate no safe harbor. It instills the belief in everyone in this country that no matter where you start in life, there's nothing you can't achieve if you work at it," he said later in his announcement video.
Biden enters the race with the kind of name recognition that makes him a de facto frontrunner. But he'll also face questions about accusations from women about unwanted touching, money, messaging, age, identity and ideology in a political environment vastly different from the one he began his career in decades ago.
Sen. Cory BookerThe New Jersey senator and former mayor of Newark declared his candidacy on Feb. 1 after spending time last year campaigning for Democrats in Iowa, Nevada, South Carolina and Mississippi.
Booker has thus far campaigned on a message of unity and collective action, promising to bring Democrats and Republicans together like he has on issues such as criminal justice reform during his time in the Senate.
"I think a lot of folks are beginning to feel that the forces that are tearing us apart in this country are stronger than the forces that tie us together. I don't believe that," Booker said on "The View" the day he announced his campaign. "So, I'm running to restore our sense of common purpose, to focus on the common pain that we have all over this country."
Gov. Steve BullockMontana Gov. Steve Bullock is most notably known for winning in 2016 as a Democrat in a state that helped elect Trump. In May, Bullock kicked off his bid as the 22nd presidential candidate to throw his hat in the ring.
"As a Democratic governor in a state Trump won by 20 points, I don't have the luxury of only talking to people who agree with me," Bullock said in his announcement video. "I go all across our state's 147 thousand square miles and look for common ground to get things done."
As governor, he expanded Medicaid to adults making less than about $17,000 per year and garnered support for abortion rights, while many other conservative states lean toward stricter laws.
Before becoming governor, Bullock served as a two-term attorney general for Montana. He fought to separate "dark money" and politics, challenging the the Citizens United decision in the Supreme Court in 2012. The Court eventually ruled against him in a 5-4 decision on American Tradition Partnership, Inc. v. Bullock. He continues to fight "dark money," according to his announcement video.
"Today we see evidence of a corrupt system all across America -- a government that serves campaign money, not the people," Bullock said
Soon after his announcement video was released, Bullock held an event at his former high school in Helena, Montana and he acknowledged the challenge of ahead of him to qualify for the debate but touted his win in a red state once more.
"The debate stage would be lacking a bit if they didn't have somebody that actually got reelected in a state Donald Trump won," he said.
South Bend, Indiana Mayor Pete ButtigiegButtigieg first made a national name for himself with a bid for Democratic National Committee chair in 2017. At 37 years old, he is the youngest candidate in the 2020 race, and could also become the first gay man to be elected president.
While he trails many of his opponents in name recognition, Buttigieg argues that he could represent a generational shift in government, and speaks frequently of issues that will affect younger Americans, such as tax reform, gun control and climate change.
"I get the audacity of somebody like me talking about running for this office, but frankly it's a leap for anybody," Buttigieg said on ABC's "This Week" in February. "And yet all of the people who had that job have been mortals who just bring their experience to the table. My experience is that of guiding a city through transformation, and I think a mayor at any level has the kind of executive frontline government experience and, by the way, problem-solving experience that we need more in Washington right now."
After signaling his intention to run when he launched an exploratory committee in January, Buttigieg officially entered the race on April 14 at a rally in his hometown of South Bend.
"The forces of change in our country today are tectonic," Buttigieg said. "Forces that help to explain what made this current presidency even possible. That's why, this time, it's not just about winning an election - it's about winning an era."
Former Secretary of Housing and Urban Development Julian CastroCastro, who served as mayor of San Antonio, Texas before spending over two years in President Barack Obama's cabinet, announced his campaign in his hometown in January.
"I'm running for president because it's time for new leadership because it's time for new energy and it's time for a new commitment to make sure that the opportunities I've had are available for every American," he said.
In 2016, Castro was vetted by Hillary Clinton to be her running mate, but the spot ultimately went to Sen. Tim Kaine, D-Va. This year, he says he is eager to restore the style of leadership the nation had under Obama.
NYC Mayor Bill de Blasio
New York City's mayor released a video on Youtube, announcing his campaign launch Thursday on ABC's "Good Morning America." He joins more than 20 Democratic candidates in the race for the White House.
De Blasio, who is in his second term, joins a crowded field of nearly two dozen Democrats seeking to move into the White House. The central theme of de Blasio's campaign will be "working people first."
He has been New York City's mayor since January 2014. In that role, he implemented universal pre-K and signed an executive order to exchange single-use plastics for compostable or recycling alternatives in an effort to reduce carbon emissions, plastic pollution and wildlife risks.
"Working Americans deserve better," de Blasio told ABC News Chief Anchor George Stephanopoulos on "Good Morning America" on May 16. "Right now the federal government is not on the side of working people, and that's because Donald Trump is playing a big con on America."
Former Rep. John DelaneyThe Maryland congressman was only seven months into his third term when he announced his candidacy in July 2017, becoming the first member of Congress to launch a bid in the 2020 cycle.
While Delaney, a millionaire entrepreneur and businessman before arriving in Congress, does not have the name recognition of the other likely candidates, he has already traveled to all of Iowa's 99 counties -- a right of passage for many caucus hopefuls -- and frequently discusses his pragmatic approach and desire to bridge political gaps.
"What the American people are really looking for is a leader to try to bring us together, not actually talk like half the country's entirely wrong about everything they believe," Delaney said on "This Week" in January, adding, "One of the things I've pledged is in my first hundred days, only to do bipartisan proposals. Wouldn't it be amazing if a president looked at the American people at the inauguration and said, 'I represent every one of you, whether you voted for me or not and this is how I'm going to prove it.'"
Rep. Tulsi GabbardDemocrat and Iraq War veteran Gabbard first announced her presidential bid in January in an appearance on CNN
"When we stand together, united by our love for each other and for our country, there is no challenge we cannot overcome. Will you join me?" Gabbard tweeted.
Early on in her campaign, the first American Samoan and the first Hindu member of Congress faced questions over her work in the early 2000's for an anti-gay organization run by her father, and her defense of Syrian President Bashar al-Assad, with whom she controversially met in 2017.
Sen. Kirsten GillibrandThe New York Democrat formally announced her presidential run on March 17 in a video posted to her verified YouTube account. In January, she had announced that she was forming a presidential exploratory committee during an appearance on CBS' "The Late Show with Stephen Colbert."
"I'm going to run for president of the United States because, as a young mom, I'm going to fight for other people's kids as hard as I would fight for my own," she said during the interview.
Gillibrand's past moderate political positions have stoked speculation that she could be a strong general election candidate, but some of her old stances, like support for gun control that once earned her an "A" rating from the NRA, could hinder her during the Democratic primaries. She has argued that her thinking on some topics has evolved since joining the Senate.
Sen. Kamala HarrisFollowing months of speculation surrounding the California junior senator, Harris officially announced her 2020 candidacy on ABC's "Good Morning America" in January.
"I love my country. I love my country," she said. "This is a moment in time that I feel a sense of responsibility to stand up and fight for the best of who we are."
If Harris were to win the 2020 presidential election, she would become the first woman and woman of color to ascend to the nation's highest office.
Former Gov. John HickenlooperHickenlooper joined the field in early March, seeking to parlay his success in growing Colorado's economy while passing environmental regulations and gun control laws into a successful presidential campaign. In a launch video, he spoke further of healing the nation's political divisions.
"I'm running for president because we need dreamers in Washington, but we also need to get things done," he says. "I've proven again and again I can bring people together to produce the progressive change Washington has failed to deliver."
Prior to his two terms as governor, Hickenlooper worked as a geologist before starting a brewery and serving as mayor of Denver, and said that the variety of experiences have one common theme.
"One thing I've shown I can do, again and again, is create teams of amazingly talented people and really address these issues that are the critical issues facing this country," he said on "Good Morning America."
Gov. Jay InsleeInslee became the first sitting governor to join the presidential field when he kicked-off his campaign in early March.
The Washington governor is currently serving his second term in Olympia after more than two decades as a member of Congress and said that while he is proud of efforts to raise the state's minimum wage and increase access to early childhood education, his presidential bid will prioritize climate change, which he labeled an "existential threat" during his launch event.
"We went to the moon, and created technologies that have changed the world," Inslee said in his announcement video. "Our country's next mission must be to rise up to the most urgent challenge of our time: defeating climate change."
Sen. Amy KlobucharKlobuchar launched her campaign on a snowy February day in Minneapolis, laying out a platform that included a constitutional amendment to overturn the Citizen's United Supreme Court decision, signing back on to the Paris climate agreement, and advocating for criminal justice reform and universal health care/
"I'm running for every parent who wants a better world for their kids," Klobuchar said at her opening rally. "I'm running for every student who wants a good education. For every senior who wants affordable prescription drugs. For every worker, farmer, dreamer, builder. For every American. I'm running for you."
The Minnesota senator is viewed favorably by some in Democratic circles for her ability to perform strongly in her home state -- part of a Midwestern region that helped President Trump to victory in 2016.
Miramar, Florida Mayor Wayne Messam
The little-known Florida mayor joined the growing list of 2020 presidential candidates, announcing his candidacy on March 28 despite facing an uphill climb for his bid.
Messam is currently the chief executive of a city of 140,000 residents -- more than the population of the city Buttigieg runs in Indiana. He is known by many Floridians for playing football for Florida State University in the 1990s. Despite his low national name recognition, Messam is confident in his chances.
"When people get elected into Washington with no local government experience, they are so high in the stratosphere that they have no concept, no consciousness of some of the local challenges that cities and communities face. And America is basically a network of cities and communities," Messam said, according to the Associated Press.
Rep. Seth Moulton
Rep. Seth Moulton, a 40-year-old Democrat from Massachusetts, formally announced his presidential bid for 2020, expanding the Democratic field to 19 candidates.
Moulton, a Marine veteran who served in Iraq, is known as an outspoken critic of his own party. He was elected to the House in 2013.
During the 2018 midterms, Moulton raised over $4 million through his Serve America PAC to support Democratic candidates running in battleground states. Before announcing his candidacy, he had already laid groundwork for his 2020 campaign, already visiting Iowa, South Carolina, New Hampshire and Nevada.
"I'm here to tell you, and to tell America, that I'm running for president of the United States," Moulton told ABC News Chief Anchor George Stephanopoulos on "Good Morning America" on April 22.
Former Rep. Beto O'RourkeO'Rourke, who rose to national prominence during his ultimately failed challenge of Texas Sen. Ted Cruz in 2018, officially announced his presidential campaign in mid-March, calling it "a defining moment of truth for this country and for every single one of us."
The former Texas congressman immediately embarked on his first ever trip to Iowa and visited Wisconsin as well during his first weekend on the trail.
Within days, O'Rourke's campaign announced it raised over $6.1 million in the first 24 hours following his announcement, topping Sen. Bernie Sanders' previous high-water mark of $5.9 million.
Ohio Rep. Tim Ryan
The Ohio Democrat, who announced his candidacy on ABC's "The View" on April 4, bills himself as a someone who can unify the progressive wings of the Democratic Party with the more middle-of-the-road working-class voters.
"We have politicians and leaders in America today that want to divide us, they want to put us in one box or the other, " he told the crowd at his kickoff rally in Youngstown on April 6. "You know, you can't be for business and for labor; you can't be for border security and immigration reform; right, you can't be for cities and rural America; you can't be for the North and the South; you can't be for men and women. I'm tired of having to choose."
Ryan, a more moderate voice in the crowded field of competitors, rose to the national political stage in 2016 when he launched a failed bid to replace Rep. Nancy Pelosi, D-California, as House minority leader. He had previously been floated as a potential candidate in the 2014 Ohio gubernatorial election.
Sen. Bernie SandersAfter a 2016 campaign that saw him amass millions of supporters even as he finished second to Hillary Clinton, Sanders entered the 2020 race in February, predicting victory and pointing to the progressive idea he had championed as an outsider during the last cycle, like Medicare-for-all and free college tuition, that have become increasingly mainstream.
In an email to supporters announcing the launch of his campaign, Sanders further took aim at President Trump, using some of the starkest language of a Democratic candidate up to that point.
"You know as well as I do that we are living in a pivotal and dangerous moment in American history," her wrote. "We are running against a president who is a pathological liar, a fraud, a racist, a sexist, a xenophobe and someone who is undermining American democracy as he leads us in an authoritarian direction."
Rep. Eric Swalwell
The New York congressman and vocal critic of the president, Swalwell officially launched his bid for the Democratic nomination on April 8, during an appearance on "The Late Show" with Stephen Colbert.
Swalwell, who stopped in several early-voting states during the leadup to his announcement, is rooting his campaign's agenda in the issue of gun control. Following his formal announcement, he held a town hall in Sunrise, Florida, with Marjory Stoneman Douglas High School students and families.
"I'm telling folks, keep your rifles, keep your shotguns, keep your pistols, we just want the most dangerous weapons out of the hands of the most dangerous people," Swalwell told ABC News Chief Anchor George Stephanopoulos on "Good Morning America" on April 9. "Most gun owners believe that."
President Donald Trump
On the same day he assumed the office of the presidency in 2017, President Trump filed preliminary paperwork with the Federal Election Committee (FEC) to qualify as a presidential candidate for 2020.
President Donald Trump's re-election campaign announced in early April that it raised more than $30 million in the first quarter of 2019, a total that outpaces all of his Democratic rivals and indicates he will be well-resourced in his bid for a second term in the Oval Office.
"Our prodigious fundraising is further proof of President Trump's clear record of accomplishment on behalf of the American people," wrote Brad Parscale, campaign manager for President Trump's re-election campaign.
Sen. Elizabeth WarrenAfter establishing a presidential exploratory committee just before New Year's, Warren officially joined the race in February with an event in Massachusetts.
"This is the fight of our lives," the senator said. "The fight to build an America where dreams are possible, an America that works for everyone. I am in that fight all the way."
A prolific fundraiser whose staffers spent time in a number of early primary states assisting other Democrats, Warren admitted in September that following the midterms she would "take a hard look at running for president," becoming one of the first major names to take steps towards a run.
Gov. Bill WeldFormer Massachusetts Gov. Bill Weld announced in April that he's officially running for president, becoming the first Republican to mount a primary challenge against President Donald Trump.
Weld, a current partner at the Mintz Levin law firm and the 2016 vice presidential candidate for the Libertarian Party, said he would have been "ashamed" if he passed on running against the president for the Republican party nomination.
"I'd be ashamed of myself if hadn't raised my hand and said, 'Count me in,'" he told ABC News shortly after his announcement. "I think that the president is a very divisive force and that's just not my style, and it's not what Americans deserve."
Marianne WilliamsonAuthor Marianne Williamson announced the launch of her campaign in Los Angeles in January after making six trips to Iowa and one to New Hampshire over the past year as she explored a bid.
Williamson is best known outside of political circles, having written a number of popular self-help books and as a "spiritual friend and counselor" to Oprah Winfrey with multiple appearances on her show and television network.
She also ran to represent California's 33rd congressional district in 2014 as an independent, finishing fourth in the open primary, after endorsements from then-Rep. Keith Ellison, former Govs. Jennifer Granholm and Jesse Ventura, and former Reps. Dennis Kucinich and Alan Grayson.
Andrew YangYang, an entrepreneur, is running a presidential campaign most commonly noted for its support of universal basic income -- a pledge to provide all Americans 18 and older with $1,000 per month.
Yang speaks frequently about both income inequality and the economic transformation that has enriched certain parts of the country while disproportionately harming regions that have failed to keep pace.
"I was stunned when I saw the disparities between Detroit and San Francisco or Cleveland and Manhattan. You feel like you're traveling across dimensions and decades and not just a couple of time zones," Yang told "Rolling Stone" in January. "None of our political leaders are willing to acknowledge the elephant in the room that is tearing our communities apart, in the form of technological change."