Joe Biden has warned Americans that "MAGA Republicans" are "trying to succeed where they failed in 2020" to subvert the will of voters in the upcoming midterms.
In a speech that comes just six days before the polls close, the US president said democracy is under attack because Donald Trump refused to accept the results of the 2020 election.
Pointing to the attack on House Speaker Nancy Pelosi's husband, Mr Biden warned Trump's false claims about a stolen election have "fuelled the dangerous rise of political violence and voter intimidation over the past two years".
Paul Pelosi, 82, was seriously injured after he was attacked with a hammer in his California home last week.
"There's an alarming rise in the number of people in this country condoning political violence or simply remaining silent," Mr Biden said. "The silence is complicity."
He singled out "ultra-MAGA Republicans" - a reference to Trump's Make America Great Again slogan - saying they are a minority but a "driving force" in the Republican Party.
This group is "trying to succeed where they failed in 2020 to suppress the rights of voters and subvert the electoral system itself", he added.
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"There are candidates running for every level of office in America, for governor, for Congress, for attorney general, for secretary of state, who won't commit to accepting the results of the elections they're in.
"That is the path to chaos in America. It's unprecedented. It's unlawful. And it is un-American."
In a country where many people vote early, more than 27 million Americans have already cast their ballots in what is the first election since the 6 January 2021 insurrection.
Five people were killed and more than 140 police officers injured on the day Trump supporters stormed the Capitol building - the seat of US power in Washington DC.
Trump has been blamed for inciting his supporters, in a bid to overturn the results of the election held a few months earlier.
Last night, Mr Biden implored voters to "think long and hard about the moment we are in", adding: "In a typical year, we are not often faced with the question of whether the vote we cast will preserve democracy or put it at risk - but we are this year."