Trump’s allegations are not new — he has sporadically claimed for years that the Democratic establishment sought to undermine Sanders in 2016, as have Sanders’ own supporters — but they come as Trump has accelerated his offensive against the Vermont senator, who continues to show strength in early polling.

Earlier this week, Trump sought to play up a feud between Sanders and Warren, who are battling for progressive voters, and his campaign has begun to single Sanders out in press releases and on social media more often rather than focusing more exclusively on Biden.

Trump has also recently stepped up his attacks on former New York Mayor Michael Bloomberg, who is pouring money into TV ads attacking Trump to boost his late-start bid.

But Sanders rejected Trump's "attempts to divide Democrats" in a statement Friday evening.

“Let’s be clear about who is rigging what: it is Donald Trump’s action to use the power of the federal government for his own political benefit that is the cause of the impeachment trial," he said. "His transparent attempts to divide Democrats will not work, and we are going to unite to sweep him out of the White House in November.”

When the trial begins in earnest on Tuesday, all senators will be required to attend each day of the proceedings for as long as they last.

But Sanders isn’t the only 2020 candidate who will be kept off the campaign trail as the impeachment trial drags on.

Sen. Elizabeth Warren (D-Mass.), whom polls have shown is within striking distance in Iowa; Sen. Amy Klobuchar (D-Minn.), who is hoping for a come-from-behind victory in the Hawkeye State, and Sen. Michael Bennet (D-Colo.), a longshot who has placed more stock in the New Hampshire primaries in less than a month, will all be sidelined by the proceedings.

The trial could be a huge boon to White House hopefuls like Biden and former South Bend Mayor Pete Buttigieg, who are clustered with Sanders and Warren at the top of the field. The senators currently running for president have all expressed disappointment at being kept off the campaign trail while pledging to fulfill their constitutional obligations and sending surrogates to campaign on their behalf.