In emotional closing arguments Tuesday, attorneys for President Trump painted the prosecution’s key witness in Mr. Trump’s hush-money trial, Michael Cohen, as the “MVP of liars,” hoping to discredit the former president’s sometime fixer as a compromised dissembler who cannot be trusted.

 “You cannot convict President Trump on any crime, beyond a reasonable doubt, on the words of Michael Cohen,” Mr. Trump’s lead attorney in the case, Todd Blanche, told the jury.

Mr. Blanche characterized Cohen as “the human embodiment of reasonable doubt … He lied to Congress. He lied to prosecutors. He lied to his family and business associates,” Mr. Blanche said of Cohen.

The Manhattan district attorney, Alvin Bragg, has charged Mr. Trump with multiple felonies for falsifying business records. Mr. Trump is accused of ordering Cohen, on the eve of the 2016 presidential election, to pay the adult film star Stormy Daniels, whose real name is Stephanie Clifford, $130,000 so she would not publicized a one time sexual encounter she claims to have had with Mr. Trump at a celebrity golf tournament at Lake Tahoe in 2006. Mr. Bragg alleges that Mr. Trump, as president, reimbursed Cohen for the hush-money payment, then fraudulently recorded the transaction as a legal expense.

Mr. Trump has pleaded not guilty to all charges and says he never had sex with Ms. Clifford.

Cohen is the one witness with direct evidence that Mr. Trump ordered the payment and knowingly reimbursed him, so discrediting his testimony is key to the defense’s strategy. Cohen was convicted of multiple felonies including lying to Congress, and spent time in federal prison, and establishing his credibility has been a challenge for prosecutors.

In his closing arguments, Mr. Blanche also appealed to the jury, asking them to set aside their views on the former president, saying that the case “isn’t a referendum on your views” of the former president. Mr. Trump is unpopular in Manhattan, where he only received 12.2 percent of the vote in the 2020 election.

“If you focus just on the evidence you heard in this courtroom, this is a very very quick and easy not guilty verdict,” Mr. Blanche told the jury. “Thank you.”

The prosecution countered, with New York County prosecutor Joshua Steinglass saying that the prosecution didn’t pick Cohen up “at the witness store.

“The defendant chose Michael Cohen to be his fixer,” Mr. Steinglass said. “He picked him for the same qualities that the defense now urges you to reject his testimony over.”

Mr. Steinglass also encouraged the jury to think of Cohen as their “tour guide” through the evidence against Mr. Trump rather than as the main witness in the case, saying that he “provides context and color to the documents.”

“Once money starts changing hands on behalf of the campaign, that’s election law — that’s federal election campaign finance violation,” Mr. Steinglass said.

The day at court is expected to run unusually late, until 7 pm. The court days have usually wrapped around 4:30 pm in the case so far. The jury could begin deliberations on Wednesday.

The courthouse was also the scene of political jockeying on Tuesday, with President Biden’s campaign holding a press conference outside the courthouse during which the two-time Oscar winner, Robert De Niro, warned a crowd of that Mr. Trump was, he said, a threat to democracy.

“I love this city. I don’t want to destroy it. Donald Trump wants to destroy not only the city, but the country, and eventually he can destroy the world,” said Mr. De Niro, who only months ago was in a courtroom battle himself in downtown New York with his former assistant. In November, a jury awarded the former assistant more than a million dollars for enduring a “toxic work environment.”

At the same presser, two former Capitol Police officers, Michael Fanone and Harry Dunn, repeated their claims of being assaulted by Trump supporters on January 6.

“I came here today to remind Americans of what Donald Trump is capable of and the violence that he unleashed on all of Americans on January 6, 2021,” Mr. Fanone said.

A spokesman for Mr. Trump’s campaign, Jason Miller, responded in a statement saying that, “After months of saying that politics had nothing to do with this trial, they showed up and made a campaign event out of a lower Manhattan trial day for President Trump.”

A Trump campaign press secretary, Karoline Leavitt, said that the Biden campaign presented as “desperate and failing” in their courthouse press conference, adding that the event was a “full-blown concession that this trial is a witch hunt that comes from the top.”