De Niro, a longtime Democrat who recently voiced an ad for Democratic President Joe Biden, attended a Biden campaign event on Tuesday outside the Manhattan courtroom with two former law enforcement officers, Harry Dunn and Michael Fanone, who were at the US Capitol when it was attacked by Trump supporters on January 6, 2021.
The remarks are part of the Biden campaign's attempt to use wall-to-wall media coverage of the Trump trial to push their own message: Trump is a danger to democracy.
Trump's campaign dismissed the event as a stunt.
Robert De Niro, argues with a Trump supporter after speaking to reporters in outside Trump's trial. (AP PHOTO)
Referring to Trump's successful 2016 run for president, Academy Award winner De Niro said Trump's candidacy was initially laughed off as a joke.
"We've forgotten the lessons of history that showed us other clowns who weren't taken seriously until they became vicious dictators," he said.
"With Trump we have a second chance and no one is laughing now. This is the time to stop him by voting him out once and for all."
If Trump returns to the White House, he said, Americans could see the civil liberties they take for granted evaporate as well as the end of elections.
"If he gets in, I can tell you right now, he will never leave," said DeNiro.
Fanone and Dunn delivered emotional remarks, saying violence at the Capitol was fuelled by Trump's lies that the 2020 election was stolen. The speakers were heckled by a Trump supporter as pro-Trump demonstrators chanted in the background.
Trump campaign officials said the De Niro event showed desperation in the Biden camp.
Spokesman Steven Cheung, taking the podium shortly afterwards, said the Biden camp was in "complete freakout mode" over Trump's resilience despite the multiple criminal cases against him.
"Joe Biden is losing nationally," said Jason Miller, another Trump spokesman.
"President Trump's numbers continue to rise. And the best that Biden can do is roll out a washed up actor."
A Reuters/Ipsos poll last week found the two men effectively tied among registered voters.
In his most biting comments, De Niro spoke of Trump through the lens of the largely Democratic city whose voters know Trump well and roundly rejected him at the polls.
"We New Yorkers used to tolerate him when he was just another grubby real estate hustler masquerading as a big shot, a two-bit playboy lying his way into the tabloids," he said.
"A clown ... No one took him seriously. They take him seriously now."
