WASHINGTON (NEXSTAR) — What was initially a bipartisan push to launch an independent investigation into the Jan. 6 riot at the U.S. Capitol now faces an uphill battle as a growing number of Republicans push back.

Senate Minority Leader Mitch McConnell of Kentucky announced Wednesday he would not support the commission.

“I’ve made the decision to oppose the House Democrats’ slanted and unbalanced proposal,” McConnell said on the Senate floor. “It’s not at all what new facts or additional investigation yet another commission could actually lay on top of existing efforts by law enforcement and Congress.”

His move came the day after House Minority Leader Kevin McCarthy, R-Calif., made the same announcement. Sen. Josh Hawley, R-Mo., also objects.

“This has not been bipartisan at all,” Hawley said, going on to say that House Speaker Nancy Pelosi, D-Calif., “has tried to set this up as a purely partisan exercise for political reasons.”

But other Republicans still support the effort, including Rep. John Katko of New York, who negotiated its terms. He called the commission nonpartisan and necessary.

“I’m very proud of it,” Katko said.

On the Senate floor Wednesday, Senate Majority Leader Chuck Schumer, D-N.Y., said Republicans are putting party over country.

“Both sides negotiated for months,” Schumer said. “Once again, they are caving to Donald Trump and proving that the Republican Party is still drunk off the big lie.”

Sen. Dick Durbin, D-Ill., said Republicans are trying to sweep the riot under the rug.

“I thought the videotape would speak for itself,” he said. “That was insurrectionist mob that took human lives … and I think we should make an official, formal record of it.”

Democrats have enough votes to pass the bill creating the commission in the House, but they will need the support of at least 10 Republicans to do the same in the Senate. The White House says it supports the commission.

The family of Capitol Police Officer Howie Liebengood, who died by suicide after responding to the riot, on Wednesday also called on Congress to launch the commission.