Senate Minority Leader Mitch McConnell said Wednesday he opposes a bipartisan plan to create a 9/11-style commission to investigate the Jan. 6 insurrection at the U.S. Capitol, dealing a setback to the proposal's chances in the U.S. Senate.

Just a day ago, McConnell, R-Ky., had signaled the party was open to the commission to investigate the Jan. 6 riot by supporters of former President Donald Trump but added he wanted "to read the fine print." That openness was short-lived.

"After careful consideration, I've made a decision to oppose the House Democrats' slanted and unbalanced proposal for another commission to study the events of Jan. 6," he said Wednesday on the Senate floor.

The announcement comes on the day the House of Representatives is slated to vote on the legislation. The measure is expected to pass easily with overwhelming Democratic and some GOP support. But McConnell's opposition to the legislation, which came the morning after Trump urged Republicans to oppose it, complicates the commission's fate in the evenly divided Senate. The bill needs 10 GOP senators to vote with all Democrats ultimately to become law.

Senate Majority Leader Chuck Schumer, D-N.Y., said Wednesday that "both sides" negotiated for months on the commission.

"At the 11th hour, the House Republican leadership turned tail, threw its own negotiators under the bus and decided to try to sabotage the commission," he said on the Senate floor. "Once again, they are caving to Donald Trump and proving that the Republican Party is still drunk off the big lie."

He reiterated that he will bring the proposal to the floor after its passage in the House — despite McConnell's position.

The commission also has support from former New Jersey Gov. Tom Kean and former Rep. Lee Hamilton of Indiana, who led the 9/11 Commission.

"As Chairman and Vice Chairman of the 9/11 Commission, unity of purpose was key to the effectiveness of the group. We put country above party, without bias, the events before, during and after the attack. We sought to understand our vulnerabilities in order to prevent future attacks or future acts of terrorism," the pair said in a statement Wednesday. "Today, democracy faces a new threat. 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. 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."

In his remarks Wednesday, McConnell pointed to ongoing law enforcement investigations that have resulted in hundreds of arrests as well as bipartisan investigations into the events of Jan. 6. He said a commission would result in duplicative efforts.

"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. "So ... 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. The facts have come out, and they'll continue to come out."

McConnell also accused Democrats of negotiating in "bad faith," from initial talks to various other features that he said were designed to "centralize control over the commission's process and conclusion in Democratic hands."

On Tuesday, House Minority Leader Kevin McCarthy came out against the legislation even though a deal on the commission was reached last week by House Homeland Security Committee Chairman Bennie Thompson, D-Miss., and the panel's ranking Republican, Rep. John Katko of New York. McCarthy had charged Katko with reaching a deal on the panel.

Trump blasted the proposed commission Tuesday, calling it a "Democrat trap" and urging Republicans to "get much tougher and much smarter."

"Hopefully, Mitch McConnell and Kevin McCarthy are listening!" he said in a statement.

Previously, both McCarthy and McConnell had expressed concerns about the panel's focus being too narrow. The commission would focus only on the events of Jan. 6. Some Republicans want any investigation to also focus on the unrest in U.S. cities last summer, including protests carried out by left-wing activists.

The measure is expected to pass the House on Wednesday evening. Schumer is then expected to introduce the legislation in the Senate.

Senate Republicans who have expressed early support for the commission's focus, include Minority Whip John Thune of South Dakota and Sens. Lisa Murkowski of Alaska, Mike Rounds of South Dakota and Mitt Romney of Utah.

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