New York (CNN) Former FBI Director James Comey asked American voters Sunday night to end Donald Trump's presidency with a "landslide" victory for his opponent in 2020.

"All of us should use every breath we have to make sure the lies stop on January 20, 2021," Comey told an audience at the 92nd Street Y on New York City's Upper East Side. He all but begged Democrats to set aside their ideological differences and nominate the person best suited to defeating Trump in an election.

"I understand the Democrats have important debates now over who their candidate should be," Comey told MSNBC's Nicolle Wallace, "but they have to win. They have to win."

Over the course of more than an hour, Comey repeatedly derided Trump's character, again likening the atmosphere around the President to what he saw in prosecuting mafia figures and suggested that Trump's tweets could eventually amount to witness tampering. Asked if Trump might be an unindicted co-conspirator in some of the crimes recently described by special counsel Robert Mueller, Comey said he didn't know, "but if he's not there, he's certainly close."

Still, Comey said he hoped that Trump would be swept out of office without being impeached. Framing the rise of Trumpism as a political ill the country needed to exorcise at the ballot, he expressed a hope that Americans would "in a landslide rid ourselves of this attack on our values."

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