(WASHINGTON) — The House on Wednesday is expected to pass a measure creating an independent commission to investigate the Jan. 6 Capitol attack, with some rank-and-file Republicans preparing to vote with Democrats and defy party leaders who warned against the effort.

Senate Minority Leader Mitch McConnell, R-Ky., on Wednesday morning came out against the measure to create a panel of five Republican and five Democratic appointees, one day after telling reporters he was undecided on the plan.

“After careful consideration I’ve made the decision to oppose the House Democrats’ slanted and unbalanced proposal,” he said on the floor.

On Tuesday, House Minority Leader Kevin McCarthy, R-Calif., called the proposal “potentially counterproductive” and “duplicative,” while the office of GOP Whip Steve Scalise, R-La., who also criticized the measure, advised Republicans to oppose it.

Senate Majority Leader Chuck Schumer, D-N.Y., has pledged to bring the measure to a vote, but it’s unclear if 10 Republicans will support the bill and allow it to advance through the chamber.

In a statement Tuesday evening, former President Donald Trump called the plan a “Democrat trap,” even though earlier this month, House Speaker Nancy Pelosi deputized House Homeland Security Committee Chairman Bennie Thompson, D-Miss., to finalize negotiations on the commission with ranking member GOP Rep. John Katko, R-N.Y., on a bipartisan basis.

“Republicans must get much tougher and much smarter, and stop being used by the Radical Left,” Trump said.

McCarthy and other Republicans who expressed wariness about the plan worried that the panel’s inquiry into the Jan. 6 Capitol riot would interfere with ongoing law enforcement efforts to pursue rioters who entered the Capitol and clashed with police officers, as well as the several bipartisan committee investigations in the House and Senate.

They also called for an expanded scope to review “political violence” in general — a reference to episodes of looting reported during the wave of racial justice demonstrations across the country last summer — and criticized the language in the proposal regarding hiring of commission staff, which mirrors the language used to establish the 9/11 Commission.

“When will the witch hunt of Donald Trump and those who support him come to an end?” Rep. Marjorie Taylor Greene, R-Ga., said on the House floor Tuesday in opposition to the commission. “We should have a commission to study the violent antifa and [Black Lives Matter] mobs.”

The proposal, like the 9/11 Commission, would require agreement between the leading Democratic and Republican members to issue any subpoenas.

“As we did in the wake of September 11, it’s time to set aside partisan politics and come together as Americans in common pursuit of truth and justice,” former New Jersey GOP Gov. Tom Kean, and former Democratic Rep. Lee Hamilton of Indiana, who served as the chairman and vice chairman of the 9/11 Commission, said in a statement Wednesday.

While many House Republicans appeared undecided on the vote Tuesday night, several dozen could side with Democrats to pass the bill, including members of the bipartisan Problem Solvers Caucus, which endorsed the measure Tuesday night.

“I don’t know why they wouldn’t want to make it more open,” undecided Rep. Brett Guthrie, R-Ky., told ABC News.

“I’m happy to put a light on all the facts and timelines,” said Rep. Don Bacon, R-Neb., who planned to vote for the measure.

Rep. Liz Cheney, R-Wyo., and other Republicans who supported Trump’s second impeachment after the Jan. 6 riot signaled support for the measure as well.

Cheney, who was expelled from House GOP leadership after her repeated condemnations of Trump and his baseless comments about the 2020 election, suggested in an interview with ABC News Chief Washington Correspondent Jonathan Karl on Friday that McCarthy ought to testify before the commission given his conversations with Trump during the riot.

McCarthy reportedly told Trump to call off his supporters during the riot at the Capitol, according to a statement from Rep. Jaime Herrera Beutler, R-Wash., who cited a conversation with McCarthy.

Herrera Beutler said Trump replied, “‘Well, Kevin, I guess these people are more upset about the election then you are."” McCarthy did not deny Trump’s comments but downplayed them in a subsequent interview about their exchange.

“I would hope he doesn’t require a subpoena, but I wouldn’t be surprised if he were subpoenaed,” Cheney said of McCarthy.

The vote on the commission comes as some Republicans have tried to minimized the violence on Jan. 6 and downplay the riot, which left several people dead, including a Capitol Police officer who died of natural causes after clashing with protestors, and one rioter who was fatally shot when trying to enter the House chamber.

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