The U.S. House of Representatives on Wednesday voted to create an independent commission to probe the deadly Jan. 6 attack on the Capitol by former President Donald Trump’s supporters, as one in six Republicans defied party leaders’ attempts to block it.

Over the past two days, House Republican Leader Kevin McCarthy and Senate Republican Leader Mitch McConnell worked to kill a bipartisan bill to establish the commission to investigate the violence that left five dead including a Capitol Police officer.

But the House voted by 252-175 to approve the commission, which was styled after the panel that probed attacks on the United States on Sept. 11, 2001. The bill now goes to the Senate where its future was uncertain.

The solid number of Republicans voting for the independent investigation -- 35 out of 211 -- signaled some cracks in the party's defense of Trump on a key vote. Trump opposes the creation of a commission.

All 10 of the House Republicans who voted to impeach Trump in January voted for the commission.

The bipartisan outcome could give Senate Republicans second thoughts about working to defeat the initiative.

House Majority Leader Steny Hoyer, a Democrat, said McCarthy "got what he asked for" in a compromise on the structure of the commission, which would be charged with wrapping up its investigation by Dec. 31. McCarthy is a close ally of Trump.

Earlier in the day, McConnell announced he would not support the House bill, calling it "the House Democrats' slanted and unbalanced proposal" and saying existing congressional investigations are sufficient.

In the 50-50 Senate - controlled by Democrats only because Vice President Kamala Harris can cast tie-breaking votes - Republicans can block the legislation. At least 60 votes are needed to advance most bills.

"There will continue to be no shortage of robust investigations," said McConnell, who in January said that the mob that attacked the Capitol was "fed lies" and "provoked" by Trump and others.

PELOSI'S BACKUP PLAN

House Speaker Nancy Pelosi, a Democrat, said she could launch regular committee hearings with "full subpoena power" to investigate the riot if Senate Republicans block the commission.

"But that's not the path we have chosen to go," Pelosi added, explaining that a bipartisan, outside investigation was needed to win the public's trust in any findings.

The 10-member commission would produce a public report including recommendations for preventing another Capitol attack. It would be charged with examining security and intelligence failures surrounding the riot in which Trump's supporters, after he delivered an incendiary speech, interrupted the formal congressional certification of Democrat Joe Biden's victory in the November election.

During debate, Republican Representative John Katko said, "An independent 9/11-style review is critical for removing the politics around Jan. 6."

Katko helped craft the legislation with House Homeland Security Committee Chairman Bennie Thompson, a Democrat.

The House bill, unveiled last week, would give Republicans equal power with Democrats in appointing commissioners and equal say over witnesses.

Senate Majority Leader Chuck Schumer said he will schedule a debate on the legislation. Schumer accused Republican leaders of "caving to Donald Trump and proving that the Republican Party is still drunk off the Big Lie" that the 2020 U.S. presidential election was stolen from Trump through massive voter fraud.

Senator Susan Collins, a Republican moderate, earlier in the day told reporters that while she favors modifications to the House bill, "I do think a commission is a good idea." Republican Senator John Cornyn left open the possibility of negotiating changes to the House bill.

House Democrats said congressional investigations are insufficient. Democratic Representative Zoe Lofgren, who chairs the House Administration Committee that has held hearings on the attack, told reporters her panel has uncovered "serious errors" leading up to the attack.

Describing a "howling mob" that called for hanging Vice President Mike Pence, Lofgren said her panel's work does not answer questions about who incited the mob.

"That's why we need a bipartisan, prestigious, top-of-the-line commission to find out what happened and why it happened," Lofgren said.

Republican Representative Marjorie Taylor Greene explained her opposition, saying on the House floor: "The media is going to use this (commission) to smear Trump supporters and President Trump for the next few years and cover up the real damage that is happening to the people of this country, which is tearing down our economy."

Trump on Tuesday urged Republicans to vote against the proposal, calling it a “trap” inspired by “the radical left.” Republican lawmakers who vote in favor of the commission risk drawing the wrath of Trump ahead of the 2022 elections in which Democrats are seeking to retain control of Congress.