Republican leaders scrambled on Wednesday to tamp down assist of their ranks for bipartisan legislation creating an impartial fee to analyze the Jan. 6 Capitol assault, because the Home moved towards a night vote.

Get together leaders within the Home, led by Consultant Kevin McCarthy of California, formally announced their opposition on Tuesday, arguing that their members mustn’t assist any accounting of the lethal pro-Trump mob that attacked Congress with out additionally learning “political violence” on the left. Then, after initially pledging neutrality, additionally they started lobbying lawmakers to vote no.

Senator Mitch McConnell, Republican of Kentucky and the minority chief, offered key backup on Wednesday, formally asserting his opposition to the fee as redundant and pointless only a day after he signaled he was open to voting for it.

“After cautious consideration, I’ve made the choice to oppose the Home Democrats’ slanted and unbalanced proposal for one more fee to check the occasions of Jan. 6,” Mr. McConnell mentioned in a speech on the Senate flooring.

Pointing to investigations already underway by the Justice Division and congressional committees, he added: “The information have come out and they’re going to proceed to return out.”

Mr. McConnell’s opposition will make it considerably tougher for Democrats to win approval for the fee within the Senate, the place they want at the very least 10 Republican votes to go it. Although his Democratic counterpart, Senator Chuck Schumer of New York, the bulk chief, pledged to place it up for a vote anyway.

Nonetheless, because the vote neared within the Home, high Republicans have been going through the potential of a wave of defections that threatened to as soon as once more drive a wedge by way of a celebration struggling to unite within the wake of Mr. Trump’s mendacious campaign to overturn the 2020 election. A big splintering could be significantly embarrassing for Mr. McCarthy, who after ousting his No. 3 last week for her views on Mr. Trump, vowed to unite the social gathering across the former president forward of the 2022 midterms.

The bipartisan Home Downside Solvers Caucus, which incorporates 29 Republicans, formally endorsed the fee late Tuesday. Different Republicans privately mentioned they have been inclined to vote “sure” in a present of solidarity with Consultant John Katko, Republican of New York, who negotiated the phrases of the fee at Mr. McCarthy’s behest, solely to have the chief flip round and trash the product.

Mr. Katko argued on Tuesday that the fee provided Congress the perfect likelihood to dispense with politics and actually resolve an assault that the majority members of Congress witnessed themselves in horrid detail and each events deemed a disastrous safety failure.

“We each distributed with our politics to do what the larger good is,” he mentioned.

Modeled after the fee that studied the Sept. 11, 2001, terrorist assaults, the 10-person panel could be tasked with exhaustively learning the causes of the assault and the intelligence and safety lapses that allowed 1000’s of pro-Trump supporters, a few of them armed, to overwhelm police and overtake the Capitol, sending the then-vice president and Congress into hiding. Its work could be quick: The laws requires the physique to supply a report, together with suggestions to stop future violence, by Dec. 31.

Home Democrats are anticipated to unanimously again the fee, and President Biden formally endorsed it on Tuesday.

Livid over Mr. McCarthy’s work to undermine it, particularly after they agreed to a number of of his key calls for in negotiations, Democrats skilled their fireplace on the chief forward of the vote. Democratic lawmakers, and even some Republicans, speculated that Mr. McCarthy’s opposition could possibly be pushed partly by an effort to stop damaging details about his personal conversations with Mr. Trump round Jan. 6 from coming to gentle at a time when he’s making an attempt to assist his social gathering retake the Home and change into speaker.

“My humble opinion is that there’s some data that he would deem troubling for the Republican Get together if it received out, and I believe he’ll do every thing attainable to stop that,” mentioned Consultant Bennie Thompson, Democrat of Mississippi, who co-wrote the fee invoice with Mr. Katko.