Amid tears from her supporters, Clinton issued a call for unity that emphasized the cultural and political milestones that she and Obama, the first black to secure a presidential nomination, represent.
"Children today will grow up taking for granted that an African-American or a woman can, yes, become the president of the United States," she said.
For Clinton and her backers, it was a poignant moment, the end of an extraordinary run that began with an air of inevitability and certain victory. About 18 million people voted for her; it was the closest a woman has come to capturing a nomination.
"Although we weren't able to shatter that highest, hardest glass ceiling this time, thanks to you, it has about 18 million cracks in it and the light is shining through like never before," she said in a speech before cheering supporters packed into the ornate National Building Museum, not far from the White House she longed to occupy again, as president this time.
Indeed, her speech repeatedly returned to the new threshold her candidacy had set for women. In primary after primary, her support among women was a solid bloc of her coalition. She noted that she had received the support of women born before women could even vote.
But her main goal was to heal the rift in the party - one that cleaved Democrats in part by class, by gender and by race.
"The way to continue our fight now to accomplish the goals for which we stand is to take our energy, our passion, our strength and do all we can to help elect Barack Obama, the next president of the United States," she said.
"Today as I suspend my campaign, I congratulate him on the victory he has won and the extraordinary race he has run. I endorse him and throw my full support behind him and I ask of you to join me in working as hard for Barack Obama as you have for me," the New York senator said in her 28-minute address. Loud boos competed with applause.
Clinton seemed almost buoyant in her address, feeding off the energy of a loud and appreciative crowd. "Well, this isn't exactly the party I planned but I sure like the company," she said as she opened her speech.
With 14 mentions of Obama's name, Clinton placed herself solidly behind her Senate colleague from Illinois, who awaits Arizona Sen. John McCain in the general election. "We may have started on separate journeys but today, our paths have merged," Clinton said.
Obama, in a statement from Chicago where he was spending the weekend, declared himself "thrilled and honored" to have Clinton's support.
"I honor her today for the valiant and historic campaign she has run," he said. "She shattered barriers on behalf of my daughters and women everywhere, who now know that there are no limits to their dreams. And she inspired millions with her strength, courage and unyielding commitment to the cause of working Americans."
Obama secured the 2,118 delegates needed to clinch the nomination Tuesday. Aides said Obama watched Clinton's speech live on the Internet. His campaign put a photo of the New York senator on its Web site and urged supporters to send her a message of thanks. Likewise, Clinton's Web site thanked her backers. "Support Senator Obama today," her Web page said. "Sign up now and together we can write the next chapter in America's story."
"As you may know, I was a boxer. And I've seen many fights go the distance," said Senate Democratic leader Harry Reid of Nevada. "But never have I seen one where everyone came out stronger - until now."
Obama could use the women and blue-collar voters who flocked to Clinton's campaign. She could benefit from his prodigious fundraising to help retire a debt of as much as $30 million. Clinton advanced her campaign at least $11.4 million; by law, she has only until the summer Democratic convention to recoup it.
Clinton has told colleagues she would be interested in joining Obama as his running mate and the Rev. Jesse Jackson, an Obama supporter, said Saturday that she had made "a powerful case for her eligibility" to be on the ticket.
Joining Clinton on stage Saturday were her husband, the former president, and their daughter, Chelsea. When she spoke, they stepped away. Her mother, Dorothy Rodham, wiped away a tear as she watched from nearby.
In deciding to "suspend" her campaign, Clinton kept some options open. She retains her delegates to the nominating convention and she can continue to raise money. It also means she could reopen her campaign if circumstances change before the Denver convention. But she gave no indication that was her intention.
