Sen. Bernie Sanders (I-VT) put Joe Biden (D) on defense hours ahead of Tuesday’s Democrat debate, blasting the former vice president’s record and doubting his ability to defeat President Trump.

Sanders has been taking aim at his presidential counterparts in recent days — a move that coincides with his steady rise in the polls.

“When you look at my record vs. Joe Biden’s record, I just don’t think that Biden’s record is going to bring forth the energy that we need to defeat Trump,” Sanders wrote alongside a video featuring his speechwriter, David Sirota, “fact-checking” four of Sanders’ recent claims about Biden:

When you look at my record vs. Joe Biden's record, I just don't think that Biden's record is going to bring forth the energy that we need to defeat Trump. pic.twitter.com/Y8UJYJT6wT — Bernie Sanders (@BernieSanders) January 14, 2020

“During a recent CNN appearance, Bernie Sanders made four powerful assertions that may have shocked many people. So we are deciding to fact check Bernie’s claims and see if they stand up to scrutiny,” Sirota said.

Sanders’ four claims were as follows:

“Joe Biden voted, and helped lead the effort, for the war in Iraq, the most dangerous foreign policy blunder in the modern history of this country.”

“Joe Biden voted for the disastrous trade agreements like NAFTA and Permanent Normal Trade Relations With China, which cost us millions of jobs.”

“Joe Biden has been on the floor of the Senate talking about the need to cut Social Security.”

“Joe Biden pushed a bankruptcy bill which has caused enormous financial problems for working families.”

The Sanders campaign rated all of his claims “100% true.”

Sanders is currently in the middle of a bubbling controversy with Sen. Elizabeth Warren (D-MA), who claims Sanders told her during a private meeting in 2018 that a woman could not win the presidency.

“Among the topics that came up was what would happen if Democrats nominated a female candidate. I thought a woman could win; he disagreed,” Warren said in a statement, confirming the claims made in CNN’s report.

Sanders has denied it.

He told CNN:

It is ludicrous to believe that at the same meeting where Elizabeth Warren told me she was going to run for president, I would tell her that a woman couldn’t win. It’s sad that, three weeks before the Iowa caucus and a year after that private conversation, staff who weren’t in the room are lying about what happened. What I did say that night was that Donald Trump is a sexist, a racist and a liar who would weaponize whatever he could. Do I believe a woman can win in 2020? Of course! After all, Hillary Clinton beat Donald Trump by 3 million votes in 2016.

Warren also expressed disappointment on Sunday after reports emerged of the Sanders campaign urging volunteers to dissuade voters from supporting her. The talking points included the claim that Warren is unable to expand the Democrat base.

“I was disappointed to hear that Bernie is sending his volunteers out to trash me,” she said. “Bernie knows me and has known me for a long time. He knows who I am, where I come from, what I have worked on and fought for.”

“Democrats need to unite our party, and that means pulling in all parts of the Democratic coalition,” she continued.

“I hope Bernie reconsiders and turns his campaign in a different direction,” she added

Tuesday’s debate will bring the top three candidates on the same stage, alongside Sen. Amy Klobuchar (D-MN), Pete Buttigieg (D), and Tom Steyer (D).