While Trump certainly hasn't escaped legal scrutiny during his time in office, his attorneys, in their efforts to delay or derail various investigations and cases, have repeatedly tried to claim the office of the presidency essentially granted him immunity. In several cases, the Justice Department has intervened on Trump's behalf, throwing its legal firepower behind his personal defense attorneys.
Upon departing office on Jan. 20, Trump would have to shift that strategy as he faces the new reality of managing his defenses as a private citizen, both with respect to pending civil cases, as well as investigations which could have both civil and criminal implications.
"There's no question that there are a number of active investigations that could implicate Donald Trump: private citizen, and lead to his indictment and prosecution," said attorney Richard Ben-Veniste, a former top prosecutor on the Watergate Special Prosecution Force that investigated former President Richard Nixon.
Experts questioned, however, the likelihood of any federal investigation into Trump being launched given the extraordinary political fallout that could come as a result. Nearly all of the current legal threats Trump could face are not criminal in nature and charging a former president with a crime is unprecedented.
Investigations in New York
One of the more significant potential legal threats Trump could face is from Manhattan District Attorney Cy Vance, who opened an investigation more than a year ago into Trump's personal and business finances.
The case started over payments to women who had alleged affairs with Trump, that he later denied through a White House spokesperson.
The office has not spelled out clearly what specific allegations of wrongdoing it is investigating, but Vance sought, through a subpoena, eight years' worth of Trump's tax returns.
Last year, the president resisted the subpoena claiming, that as a sitting president, he could not be criminally investigated.
The U.S. Supreme Court recently rejected the broad immunity claim that the president's attorneys asserted.
The DOJ, on Trump's behalf, then asserted in federal court that the subpoena was too broad and amounted to political harassment. Just last month, a three-judge panel rejected that claim. The government has sought review with the Supreme Court, which is now considering that petition.
New York Attorney General Letitia James separately announced in August that she was investigating whether Trump and the Trump Organization improperly manipulated the value of certain assets to secure loans and obtain tax benefits to which they otherwise would not have been entitled.
The investigation includes questions about involves at least four properties, including the Seven Springs estate in Westchester, New York originally built by Eugene Meyer, a former publisher of the Washington Post. James is investigating the estate's conservation easement, otherwise known as a legal agreement that limits use of land for conservation purposes, and whether it was inflated "for the purpose of taking a larger tax deduction that would otherwise have been permitted," a lawyer in the attorney general's office said in August.
The president's son, Eric Trump, who is currently running the business, sat for a deposition in the investigation last month. ABC News has also learned several key members of the president's company, the Trump Organization, also sat for deposition with James' office. The Trump Organization has denied any wrongdoing.
Benefitting from the presidency?
Attorneys general in both Washington, D.C., and Maryland have an ongoing lawsuit against Trump alleging he unlawfully used the office of the presidency to benefit his personal finances.
Their suit accuses Trump of violating the emoluments clause of the Constitution, which prohibits accepting gifts from foreign governments, with the attorneys general specifically citing foreign patrons to Trump's hotel in the nation's capital and other properties.
The U.S. Department of Justice Trump sued to block investigators efforts to subpoena Trump-related businesses his business and appealed for the Supreme Court to intervene, but the court has not yet decided whether to take up the case.
Defamation lawsuits from sexual misconduct accusers
The president is being sued for defamation by two women who have alleged they were sexually assaulted by Trump, Summer Zervos and E. Jean Carroll.
There are no criminal charges associated with either case and statutes of limitations have long since expired.
Zervos was a contestant on "The Apprentice" who alleged Trump groped her in a Beverly Hills, California, hotel on two occasions in 2007.
Carroll, a former Elle advice columnist, alleged he raped her in a department store dressing room in the mid-1990s.
Trump has denied both accusations, but in those denials, the women said he defamed them.
The president has unsuccessfully tried to argue he is immune from such lawsuits while in office and the Justice Department sought to intervene in the case brought by Carroll, but that effort was recently rejected by a federal judge.
The Justice Department tried to substitute for Trump as the defendant in the defamation case, citing a law that shields federal employees from liability for conduct committed in the course of their jobs. A federal judge rejected the attempt after Carroll's attorneys had argued Trump made the allegedly defaming statements outside the scope of his job as president.
The Justice Department has not said whether it will appeal the judge's order.
Michael Cohen, the 'hush money' affair and the SDNY
Another potential legal issue for Trump is a case related to the "hush money" payments to women who have alleged affairs with Trump. The payments were arranged by the president's then attorney Michael Cohen.
As a part of his August 2018 guilty plea with the U.S. Attorney's Office in the Southern District of New York, among the charges to which he pleaded guilty, Cohen said he acted at the direction of then-candidate Trump when he made a payment to adult film actress Stormy Daniels and arranged with a media company to pay former Playboy model Karen McDougal for her story.
Prosecutors said the payments were part of an illegal campaign finance scheme and Cohen said buying their silence was "for the principal purpose of influencing the election."
Cohen told the court that he made the arrangements for those hush money deals "in coordination with and at the direction of a candidate for federal office," referring to then-candidate Trump.
The plea agreement memorably identified Trump as "Individual 1," raising the specter that Trump might be considered an unindicted co-conspirator in the case, and whether, when he no longer has the protection of the presidency, prosecutors might want to pursue a case against him.
It's not clear whether the Justice Department, under new leadership, might seek to revisit the matter, following Trump's exit from the White House, though Harvard law professor Mark Tushnet told ABC News he would be "shocked" if they did so.
"There's no question that he's at legal risk and probably, in some sense, substantial legal risk, sort of, on the merits," Tushnet said. "But you have to take into account the standard language is 'prosecutorial discretion' about which well-founded charges you decide to bring and I think it would be a very bad exercise of discretion to bring charges against him."
Trump's tax bill
In September, the New York Times reported on more than two decades worth of tax return data for the president. According to the article, the IRS was zeroing in on a $72.9 million tax refund Trump applied for and received in 2010.
The Times said the data they obtained also showed Trump has a $100 million tax payment coming due in 2022 and more than $100 million more that he would be forced to pay the IRS should he lose his dispute over the 2010 refund.
While Trump and his attorneys have broadly denied the veracity of the Times investigation, they have not denied specific details related to the audit or the tax bills coming due and instead accused the paper of offering a "selective picture" of Trump's tax payments.
Political dangers of prosecuting Trump and questions of a 'self-pardon'
Legal experts who spoke to ABC News said it's possible the Justice Department, under new leadership, would consider investigating Trump if prosecutors see potential federal violations surface through the ongoing or other state investigations.
During the campaign, Biden said such a prosecution against a former president would be "probably not very good for democracy" but added he would not intervene if such a case was brought against Trump.
"The Justice Department is not the president's private law firm," Biden said in August. "The attorney general is not the president's private lawyer. I will not interfere with the Justice Department's judgment of whether or not they think they should pursue the prosecution of anyone that they think has violated the law."
Such a politically fraught decision, then, would instead likely be in the hands of Biden's eventual pick for attorney general -- weighing whether to mount a public case against an individual who netted more than 71 million votes in the most recent presidential election.
"I would expect that they would take that into consideration even without the numbers and nature of the support for Trump just because it's always been thought of to be more of a banana republic thing for the incoming administration to prosecute the outgoing administration," said Daniel Richman, a law professor at Columbia Law School. "I don't think it's just about voters, I think it's also about norms and expectations of a peaceful and straightforward transitions."
A separate conversation in legal circles is whether Trump might seek to neutralize any potential for a federal investigation by preemptively pardoning himself before leaving office.
During the fast-moving developments of the Russia investigation in 2018 Trump tweeted he had "the absolute right to PARDON myself," though such a move has not been constitutionally tested before.
In bolstering the idea Trump could preemptively pardon himself, experts point both to Gerald Ford's pardon of Richard Nixon before he was charged with a crime as well as a 19th century ruling by the U.S. Supreme Court where it held that a pardon "may be exercised at any time after" the commission of a crime, "either before legal proceedings are taken or during their pendency or after conviction or judgment."
"There's no language in the Constitution explicitly prohibiting a self-pardon," Tushnet, the Harvard law professor, said. "But of course there is a sort of background principle that no person should be a judge in his or her own case and a self-pardon clearly is inconsistent with that principle.
"You'd have to have a lot of confidence that the pardon would stick because if he does it and it doesn't stick the mere doing of it would be part of a case against him," Richman said.
A separate theory legal experts raised is that Trump could resign in the days before Jan. 20 and Vice President Mike Pence, assuming the powers of the presidency, would instead extend Trump a full pardon.
Such a move, however, would not extend to any state charges Trump might eventually face.