Senate Minority Leader Mitch McConnell said Wednesday on the Senate floor that he would not back a bill that would form a 9/11-style commission into the January 6 Capitol riot.

'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,' McConnell said.

His move comes after House GOP leadership made the same decision, with a House vote expected Wednesday afternoon.

McConnell's actions almost definitely doom the legislation, as the Senate leader has had a public falling out with former President Donald Trump, since he refused to concede the election, and especially after the insurrection.

However, McConnell also voted to acquit Trump on impeachment charges over inciting an insurrection.

Directly after the February impeachment vote, McConnell said, 'former President Trump’s actions preceding the riot were a disgraceful dereliction of duty,' and hinted he believed the ex-president could be criminally charged.

'As everybody surely knows, I repeatedly made my views about the events of January 6 very clear. I spoke clearly and left no doubt about my conclusions,' McConnell said on the floor Wednesday.

The Kentucky Republican pointed out that law enforcement had made 445 arrests and that federal authorities expect to arrest at least 100 more rioters. He also pointed out that several Senate committees were investigating the insurrection.

'So there is, has been, and there will continue to be no shortage - no shortage of robust investigations by two separate branches of the federal government,' McConnell said.

McConnell said it's 'not at all clear' what new facts the commission could unearth.

'The facts have come out and they'll continue to come out,' he said. 'What is clear is that House Democrats have handled this proposal in partisan bad faith, going right back to the beginning, from initially offering a laughably partisan starting point to continuing to insist on various other features under the hood that are designed to centralize control over the commission's process and its conclusions in Democratic hands.'

Senate Majority Leader Chuck Schumer objected to McConnell's characterization of the bill being too 'slanted.'

'Speaker Pelosi bent over backwards to meet wheir needs and their asks,' Schumer told reporters Wednesday.

'It will be on the floor and we'll see where our Republican friends stand,' he also said. 'Will they stand with truth or will they stand with the big lie?'

Moderate Senate Republicans still seemed open to the commission, but likely not enough to override a filibuster.

'I also think it's important that this be independent and non-partisan and that means that we should make sure that the work is done this year, and does not go over into the election year,' Sen. Susan Collins told reporters. 'There's plenty of time to complete the work.'

On Tuesday, House Minority Leader Kevin McCarthy said he was against the creation of an independent, bipartisan commission to investigate the deadly Jan. 6 insurrection at the Capitol because it didn't look at 'interrelated forms of political violence' such as Antifa and Black Lives Matter.

On Tuesday night, House Republican Whip Steve Scalise encouraged members of the party to vote against it, sending out a note saying, 'Leadership recommends a NO vote.'

A group of moderate Republicans are still expected to back the bill.

Politico Playbook reported Wednesday that at least 12 Republicans say they'll vote for the bill, including New York Rep. John Katko, who negotiated the deal with Democrats before House Minority Leader Kevin McCarthy announced Tuesday he was against the final version of the legislation.

Other members planning to buck leadership include Rep. Liz Cheney, who was pushed from her leadership post and replaced with the more Trump-friendly Rep. Elise Stefanik last week, as well as other impeachment backers like Reps. Adam Kinzinger, Anthony Gonzalez and Jaime Herrera Beutler.

Playbook reported that at least three GOP members who didn't vote for Trump's impeachment - Reps. Don Bacon, Dave Joyce and Andrew Garbarino - are expected to give a green light to the commission.

Overall, the number of Republican defections is expected to be between 20 and 30.

During Wednesday's House floor debate, Republican Rep. Tom Cole applauded the work of Katko, saying it's now a 'much better bill' but said he still had reservations about it.

House Democrats were aghast at the Republicans' about-face.

'The distinguished minority leader sent a letter to Speaker Pelosi asking for an equal five-five ratio in appointments of Democrats and Republicans on this ... commission. He got it. He asked for co-equal subpoena power. He got it. He asked for no inclusion of findings or other pre-determined conclusions, which ultimately should be rendered by the commission itself. He got it,' said Rep. Jim McGovern, a Massachusetts Democrat. 'Now maybe he didn't think he would.'

'But Chairman [Bennie] Thompson and Ranking Member Katko ... came to a deal. A genuinely bipartisan deal, to look into the horrific acts of what happened in this chamber on January 6,' McGovern continued. 'I was here. They were not ordinary tourists who came in here, my colleagues on the Republican side, who are here today, there are pictures of them helping to barricade the doors, they know exactly what happened on January 6.'

McGovern urged Republicans to vote for the bill on behalf of Congressional staff and the Capitol Police, who he said were 'traumatized' by what took place.

'And our response to all of this is: well, let's move on, let's not do this - in spite of a truly bipartisan negotiation and a bipartisan commission,' he continued.

'This is so disappointing,' McGovern said.

'Don't talk to us about bipartisanship and when you get it, turn your back on it,' he added. 'I'm sick and tired of those who want to hover around mistruths and lies and spread conspiracy theories. What happened 133 days ago can never be normalized.'

Rep. Adriano Espaillat, a New York Democrat, said, 'We must ensure that these sacred halls will never be overrun by racist thugs against our democracy.'

While Rep. Steve Cohen, a Tennessee Democrat, brought along a sign showing Jack Nicholson from 'A Few Good Men' with his quote, 'You can't handle the truth' written on it.

'If we don't have this commission and reveal the truth, it will happen again,' Cohen said. 'If you can't handle the truth. Get the truth out.'

House Speaker Nancy Pelosi's spokesman Drew Hammill suggested McCarthy's move to eliminate Centers for Disease Control and Prevention safety protocols from the House - in short, allow members to go mask-less - was a way to stave off an 'internal mutiny' over the January 6 bill.

'Minority Leader McCarthy’s resolution is a sad stunt to distract from the reality: that the House Republicans are descending into pure chaos,' Hammill said in a statement. 'Today, the House is voting on a bipartisan commission to establish the truth of the January 6th insurrection and to prevent similar future attacks. After announcing his new opposition to this commission, which was negotiated and called for by his own members, the Republican Minority Leader is throwing everything at the wall as he tries to stave off internal mutiny.'

The bill creates a rift with former President Donald Trump, who McCarthy has embraced again after initially criticizing the leader over his role in stoking the riot.

'McCarthy knows a commission creates a conflict with Trump so he threw his ranking member under the bus,' a senior GOP aide told The Daily Beast Tuesday in reference to Katko.

McCarthy said he wanted the new panel to look beyond the violent uprising by supporters loyal to Trump, who were trying to stop the certification of President Joe Biden's election.

He pushed to have the new commission also investigate other groups, namely Black Lives Matter, which protested police violence in the aftermath of the death of George Floyd.

Pelosi ripped McCarthy Tuesday after learning of his change of position.

'I'm very pleased that we have a bipartisan bill to come to the floor, and it's disappointing but not surprising that the cowardice on the part of some on the Republican side not to want to find the truth,' she told reporters in the Capitol.

Asked if she anticipated getting GOP support for the commission – which has gotten unequivocal backing from Cheney – Pelosi responded: 'We'll see.'

McCarthy said that given the 'shortsighted scope that does not examine interrelated forms of political violence in America, I cannot support this legislation.'

Scalise's memo to Republicans said the commission wouldn't be able to investigate 'the political violence leading up to and following the attack on the 6th, including the June 2017 shooting at the Republican Congressional baseball practice, and the deadly attack on Capitol Police on April 2, 2021.

Scalise was wounded during the Congressional baseball practice attack.

The shooter, who died from wounds suffered in the attack, was a supporter of Bernie Sanders' 2016 presidential run.

The more recent Capitol car attack was carried out by a man who was a follower of the Nation of Islam.

With House GOP leadership firmly against the bill, it all but ensure this week's vote will have less support in the House, and dims its chances in the evenly divided Senate.

McCarthy and Scalise's stance came despite their own appointed negotiator, Katko, reaching an agreement with Democratic Rep. Bennie Thompson of Mississippi on the commission.

'While Ranking Member Katko negotiated in earnest to improve upon previous proposals, Speaker Pelosi delayed for months and prevented the inclusion of a wider investigatory scope, proving her main concern is politics over solutions,' Scalise wrote in his memo.

Language to create the commission gives subpoena power – and either the majority or minority could exercise it.

One added hang-up for McCarthy: he may be required to testify to the commission owing to his Jan. 6th phone call with Trump where he reportedly yelled for the president to send the MAGA mob home.

There were multiple reports in the aftermath of the riot on an angry phone call between McCarthy and Trump, with McCarthy telling Trump: 'Who the f--k do you think you are talking to?'

Lawmakers say Trump told McCarthy: 'Well, Kevin, I guess these people are more upset about the election than you are.'

Trump repeatedly referred to McCarthy, who aims to be speaker if Republicans take over the House, as 'My Kevin.'

The two met at Mar-a-Lago after Trump left the White House to discuss strategy.

Pelosi came out initially for a panel where Democrats would hold ultimate control, but the final deal is split evenly, with McCarthy and other leaders all getting an even hand in appointing commissioners.

McCarthy said Pelosi 'wasted time playing political games,' which allowed other agencies to 'pick up the slack.'

The Biden administration on Tuesday came out with its official statement backing the commission.

'The attack on the Capitol on January 6, 2021, was an unprecedented assault on our democracy, an effort to undo the will of the American people and threaten the peaceful transition of power,' according to the statement.

'While the Federal Government has already begun taking action to improve the safety and security of the U.S. Capitol, the Administration supports the proposed bipartisan, independent National Commission to study and investigate the facts and circumstances surrounding the January 6, 2021 attack on the Capitol. The Nation deserves such a full and fair accounting to prevent future violence and strengthen the security and resilience of our democratic institutions.'