With much fanfare, upstate New York Republican Rep. John Katko negotiated a deal with Democrats to launch a 9/11-style investigation of the Jan. 6 attack on the U.S. Capitol.

But now leaders in his own party are rejecting that plan.

The Democrat-controlled U.S. House approved the commission proposal Wednesday evening. Only 35 Republicans backed the measure, with 175 Republicans voting against it.

Earlier this year, Rep. Kevin McCarthy, the top House Republican, tasked Katko with working out a deal.

After extensive talks, Katko and his Democratic counterpart on the House Homeland Security Committee brokered an agreement for the 10-member panel, split evenly between Republican and Democratic appointees.

The commission's goal would be to craft a report by year’s end about the violent January attack, where supporters of Donald Trump tried to stop the certification of Joe Biden’s victory in the presidential election.

“This is about facts. It’s not partisan politics,” Katko said in a floor speech ahead of the House vote.

However, McCarthy and Senate Minority Leader Mitch McConnell balked at the deal, even though Democrats said McCarthy was regularly updated on negotiations and that the legislation includes much of what he wanted.

McCarthy now said any investigation should also look at violence by left-wing groups like Antifa.

Rep. Paul Tonko, an Albany-area Democrat, blasted the Republican leader.

“I find it deplorable that Leader McCarthy would reject his own party’s work,” he said.

Katko argues the deal he negotiated is fair, but he is so far not criticizing his fellow Republicans on Capitol Hill for their opposition.

“I absolutely respect my colleagues' decisions to take a different point of view. Politics is not always about everybody agreeing,” he said Tuesday.

Though the bill has passed through the House, in the evenly split Senate it will need Republican buy-in. With McConnell objecting, it is unclear how many GOP votes the commission plan could get, meaning the panel's fate is uncertain.