Senator Bernie Sanders is planning to mount an aggressive campaign to counter potential attempts by President Trump to delegitimize the results of the November election, warning that Democrats and Republicans alike must do “everything that we can to prevent that from happening.”
In a phone interview on Monday evening, Mr. Sanders said he would spend the next six weeks urging the country to prepare for a “nightmare scenario” in which Mr. Trump declares himself the winner of the election and refuses to step down even if he loses.
As part of his effort, he is set to deliver a speech in Washington on Thursday — his first in-person appearance related to the election since before he dropped out of the presidential race — to outline in stark terms the danger that he says Mr. Trump poses to the nation’s democracy.
“We are living in an unprecedented and dangerous moment — extremely dangerous moment — in American history,” Mr. Sanders said. “And what this speech is going to be about is whether or not the United States of America will continue to be a democracy and a nation ruled by law and our Constitution.”
In the interview, Mr. Sanders said that he thought there was an “excellent chance” that Joseph R. Biden Jr., the Democratic presidential nominee, would win the election, but that he was worried that the Biden campaign was not doing enough to reach “nontraditional voters,” including young people and Latinos.
He said he was planning to hold a virtual town hall event on Tuesday with Julián Castro, the former housing secretary under President Barack Obama.
Mr. Trump, who has consistently trailed Mr. Biden in national and swing-state polls, has spent months trying to sow doubt about voting and the election. The president has claimed without evidence that mail voting will lead to “the greatest Rigged Election in history”; has urged people in North Carolina to illegally vote twice to stress-test the election system; and has even suggested delaying the election, which he cannot do on his own.