Republican leaders are trying to sink legislation establishing an independent commission on the deadly Jan. 6 attack on the Capitol that would probably scrutinize former president Donald Trump’s role in the riot and his conversations with Republican lawmakers that day.

The bill passed the House on a 252-to-175 vote Wednesday with 35 Republicans supporting the measure, but its chances of clearing the Senate dimmed after Senate Minority Leader Mitch McConnell (R-Ky.) came out against the bill earlier in the day.

He said he opposes the legislation because it is a “slanted and unbalanced proposal” a day after he said his members were open to voting for the plan but needed a chance to read the “fine print.”

In between those comments, Trump released a statement Tuesday evening slamming the bill and decrying it as a “Democrat trap” while urging McConnell and other GOP leaders to start “listening.”

The House on May 19 debated whether to pass legislation to create an independent commission tasked with investigating the Jan. 6 attack on the U.S. Capitol. (The Washington Post)

“It’s not at all clear what new facts or additional investigation yet another commission could actually lay on top of existing efforts by law enforcement and Congress,” McConnell said on the floor Wednesday.

Several questions remain about the attack, however, including to what degree it was coordinated as well as details about what Trump was doing while it was taking place.

The attempts to undermine support for the commission by McConnell and House Minority Leader Kevin McCarthy (R-Calif.) are the latest evidence of the party’s continued loyalty to Trump and the fear among its leaders that crossing him will imperil their positions and the GOP’s efforts to win back both houses of Congress next year.

Senate Minority Leader Mitch McConnell (R-Ky.) on May 19 said that he will oppose legislation to create a commission to investigate the Jan. 6 Capitol attack. (U.S. Senate)

While McConnell and McCarthy both slammed the deal as partisan and duplicative, despite its being struck between the Democratic and Republican leaders of the House Homeland Security Committee, other Republicans were more direct about their concerns that the commission’s work would be politically problematic for the party.

“Anything that gets us rehashing the 2020 election, I think, is a day lost on being able to draw contrast between us and the Democrats’ very radical left-wing agenda,” said Sen. John Thune (R-S.D.), the minority whip.

The number of House Republicans who supported the bill, however, showed that some members of the party believe the investigation is needed even if most viewed it as a political non-starter.

The legislation is modeled on the commission created to examine the Sept. 11, 2001, terrorist attacks, and its two leaders, Tom Kean and Lee Hamilton, came out in support of the bill Wednesday.

“The January 6 attack on the U.S. Capitol was one of the darkest days in the history of our country. Americans deserve an objective and an accurate account of what happened,” they said in a statement.

The proposal also received support from the family of U.S. Capitol Police officer Howard Liebengood, who died by suicide days after a pro-Trump mob stormed the Capitol.

In recent weeks, some House Republicans have downplayed the events of Jan. 6, with one lawmaker suggesting images from inside the Capitol resembled a normal tourist visit and another questioning how anyone could be sure the rioters were Trump supporters.

But videos from that day show an angry mob, many clad in Trump’s signature “Make America Great Again” gear, waving Trump flags, violently beating and dragging police officers as they breached security barriers, climbed through broken windows and entered the Capitol.

They marched through the halls chanting “Hang Mike Pence” and “Where’s Nancy?” as they pounded on the door of House Speaker Nancy Pelosi (D-Calif.), terrorizing her staffers.

The assault on the Capitol resulted in the deaths of five people, and 140 police officers were injured, many severely, including one who lost an eye.

Trump was impeached on charges of inciting the riot with his false claims that the election was stolen and his remarks at a rally that day when he told his supporters to walk down to the Capitol and tell Republicans they should not certify Joe Biden as the winner of the presidential election. The Senate voted to acquit Trump in February.

Wednesday’s House vote exposed tension among the chamber’s Republicans over how to respond to Jan. 6.

On Friday, House Homeland Security Committee Chairman Bennie Thompson (D-Miss.) and the panel’s top Republican, Rep. John Katko (R-N.Y.), announced they had a deal on commission legislation.

McCarthy quickly distanced himself from that agreement, raising questions about why he empowered Katko, who voted to impeach Trump, to strike a deal if he wasn’t going to support it in the end.

“Thanks for not throwing me under the bus, Kevin,” Katko said sarcastically during a private GOP meeting Tuesday, according to a Republican aide who spoke on the condition of anonymity to discuss the private discussion.

“There may have been a miscommunication,” Rep. Ken Buck (R-Colo.), who opposed the bill, said about the situation between Katko and McCarthy. “Clearly something went awry.”

Katko defended the legislation during the floor debate Wednesday and urged colleagues from both sides of the aisle to support the proposal, which he noted is similar to a bill introduced earlier this year by Republicans.

“I encourage all members, Republicans and Democrats alike, to put down their swords for once, just for once, and support this bill,” he said.

The 35 Republicans who supported creating the commission represent a far greater number than the 10 who voted to impeach Trump, showing some division within the conference.

Only four Republicans spoke against the bill during floor debate.

Many Republicans argued this week that the legislation would establish a partisan investigation despite the fact that it would have an equal number of Republicans and Democrats, five on each side, but they were careful not say they opposed the idea of a commission. Many said they wanted it to be empowered to also investigate protesters at racial justice rallies across the country this past summer.

“Hanging Judge Nancy Pelosi is hellbent on pushing her version of partisan justice complete with a handpicked jury that will carry out her predetermined political execution of Donald Trump before law enforcement officials have completed their investigation,” Rep. Greg Pence (R-Ind.), the brother of former vice president Mike Pence, said in a statement Wednesday.

The Indiana congressman was with the vice president during the Jan. 6 attack. They huddled together inside a Capitol office guarded by Mike Pence’s Secret Service detail and later took an unknown evacuation route to a secure room in the Capitol complex.

Democrats and some Republicans have noted that McCarthy, who did not speak during floor debate on the bill, is urging a no vote on legislation that would create a commission that would probably call him to testify because he spoke to Trump that day, pleading with him to publicly call on the mob to leave the Capitol.

“He absolutely should,” Rep. Liz Cheney (R-Wyo.) said during a recent interview with ABC News. “And I wouldn’t be surprised if he were subpoenaed. I think that he very clearly . . . said publicly that he’s got information about the president’s state of mind that day.”

House Republicans kicked Cheney out of her leadership post this month after she continued to challenge Trump over his false claims that the election was stolen and for his role in the riot.

McConnell’s opposition came after he told reporters Tuesday that Senate Republicans were “undecided” about the commission.

On Wednesday, he said his reading of the bill led him to oppose the creation of the panel.

“After careful consideration, I’ve made the decision to oppose the House Democrats’ slanted and unbalanced proposal for another commission to study the events of January the 6th,” he said on the Senate floor.

McConnell’s opposition makes it more likely that enough Republican senators will band together against the commission legislation to block it from proceeding. The bill will need to garner 60 votes in a 50-50 Senate to clear a filibuster.

Seven Senate Republicans voted to impeach Trump after the Jan. 6 riot, and those senators are considered likely to back the commission. But McConnell’s stance is likely to prompt other Republicans to close ranks and oppose the bill.

Thune declined to say Wednesday whether he thought 10 Republicans could ultimately support the commission. But he suggested to reporters it would be an uphill climb for Democrats.

“We have different members who are in different places, but I would say that there is a skepticism about what’s happening in the House right now and whether or not what comes out is a proposal that’ll be fair,” he said.

In a sign that attracting 10 Republicans could be difficult, Sen. Mike Rounds (R-S.D.) went from giving the commission tentative support on Tuesday to declaring himself opposed on Wednesday.

Speaking to reporters shortly after McConnell made his views known, Rounds said he changed his mind after hearing from McCarthy at a breakfast hosted by Sen. Roy Blunt (R-Mo.) Wednesday morning, where he shared concerns that Democrats would have too much control over the commission’s staff and that it would take too long to get started — pushing the probe into an election year.

“I really thought that there was a hope that we would find a bipartisan path forward in an expedited manner,” Rounds said. “It doesn’t appear to me that that’s in the cards.”

Even some of the Republicans who voted to impeach Trump declined to explicitly endorse the commission Wednesday.

Sen. Mitt Romney (R-Utah), for instance, reserved judgment and said he would support the bill only if it was “truly bipartisan.”

Senate Majority Leader Charles E. Schumer (D-N.Y.) said the Senate will vote, forcing Republicans to take a stand.

“The only way to stop these lies is to respond with the truth, with facts, with an honest, objective investigation of what happened that day. An independent commission can be the antidote to the poisonous mistruths that continue to spread about January 6th,” Schumer said on the Senate floor.

In February, McConnell voted to acquit Trump of impeachment charges that he incited the attack on the Capitol. The minority leader condemned Trump’s behavior after the vote saying he was “practically and morally responsible’ for the attack.”

But since that time, McConnell has avoided addressing the topic, answering questions about Trump’s continued role in the party by saying he is focusing on the future.

On Wednesday, he cited ongoing federal investigations into the Jan. 6 attack as a reason he opposes the commission.

While McConnell suggested the commission would be duplicative of other investigations, the panel as envisioned by the House would have a larger scope than the Senate probe currently underway — which is closely focused on the security of the Capitol campus and the security failures that prompted the breach. The prosecutions, meanwhile, are focused on the discrete criminal actions of individuals and groups who participated in the riot.

The House bill envisions that the commission would not only look at the security of the Capitol but also “the influencing factors that fomented such attack on American representative democracy while engaged in a constitutional process” and make recommendations for action. It could, for instance, seek to find out what role Trump played in encouraging the attack, as well as his response once it was taking place — something that could lead to members of Congress themselves being subpoenaed.

Meagan Flynn and Marianna Sotomayor contributed to this report.