Washington, United States: Donald Trump assumes the mantle of the US presidency under an unprecedented cloud of litigation that could weigh on his ability to govern after this week's shock election. 

Just as the newly minted president-elect visited the White House and Capitol Hill on Thursday, two thousand miles away his lawyers were in a California courtroom battling over evidence and jury instructions in a fraud trial over the defunct Trump University, which stands accused of defrauding students.

On the campaign trail, Trump disparaged the judge in the same case, Gonzalo Curiel, as a "Mexican" and a "hater," and Trump's attorneys want such remarks excluded as evidence. 

Trial begins in 18 days, meaning Trump could be sworn in as a witness in the case well before he is sworn in as president.

  - Scores of cases -

In New York, the billionaire developer, a famous legal pugilist with a lifetime's worth of business enemies and sparring partners, is facing a case brought by Attorney General Eric Schneiderman, also over Trump University, as well as a libel case from a political consultant and lawsuit from a protester claiming he was assaulted outside Trump Tower.

Then there is his pending IRS tax audit. And a case in Chicago accusing his campaign of spam text messages. And a breach of contract case a Trump company brought in Washington -- Trump was accompanied by a Secret Service agent to a recent deposition in that case, according to court papers.

That is just a sample of the private legal matters the sitting president will have on his plate.

"This is going to be one of the many unprecedented things about a Trump presidency," Louis Seidman, a scholar of constitutional law at Georgetown University, told AFP.

According to USA Today, over the past three decades Trump and his business entities have been involved at least 3,500 legal actions in federal and state courts, ranging from high-stakes business clashes to personal defamation lawsuits.

In just the year following the announcement of his candidacy in June of 2015, at least 70 cases were filed, split evenly between those Trump brought and those filed against him, according to the newspaper.

The Trump Organization and an attorney for Trump in California did not respond to requests for comment.

 - No absolute immunity -

Despite their power, US presidents can and have been dragged into the courts. The Supreme Court held in 1982 that former president Richard Nixon was immune from liability for damages based on his official acts. 

Fifteen years later, however, the court found that Bill Clinton could face civil litigation for acts occurring before his presidency in a sexual harassment suit brought by Paula Jones. Clinton went on to survive impeachment in 1999 over accusations that he had lied and obstructed justice during the Jones case.

"The law stands with what the court decided in that case," Clinton's attorney at the time, Bob Bennett, told AFP. "And they said the president does not have absolute immunity in civil suits."

Seidman said courts were often expected to adjust their schedules to suit the many pressures and demands on serving presidents. The Supreme Court has also never decided whether a president may face criminal prosecution, he added.

Trump's legal entanglements will almost certainly be a factor in his ability to govern, said Seidman.

"Disentangling him from that business is going to be close to impossible," said Seidman. "There are going to be constant legal distractions."

Trump's ability to govern under such circumstances will depend on the resources he can bring to bear, said Seidman, adding that Trump's courtroom battles as president are in many cases likely to be driven by political rather than legal forces.

"On the one hand, he is coming into office with all the levers of power," he said, noting that Republican party will soon control the executive branch and both houses of Congress. 

"On the other hand, he is also coming into office as the least popular president in American history, with less than a majority of the popular vote and half of the country despising him."

"The real risk is that he might react to those sorts of problems by trying to exercise still more power," said Seidman. "A lot of this is going to depend on how good of a politician he is."