Sen. Susan Collins, R-Maine, arrives as senators rush to the chamber for votes ahead of the approaching Memorial Day recess, at the Capitol in Washington on Wednesday. Credit: J. Scott Applewhite / AP

WASHINGTON — U.S. Sen. Susan Collins is leading a last-minute push to salvage a bipartisan commission on the Jan. 6 Capitol insurrection as Democratic leaders in the Senate push for an uphill Thursday vote on the measure.

Republicans looked poised to block the legislation despite the bipartisan effort led by the Maine senator to salvage the bill and another by the mother of Brian Sicknick, the Capitol Police officer who collapsed and died after the siege.

Senate Majority Leader Chuck Schumer, D-New York, has set up a Thursday procedural vote on the bill, challenging Republicans to support it after 35 of their GOP colleagues voted for it in the House. But it was unlikely that Democrats would be able to win the 10 Republican votes necessary to authorize the independent investigation, a remarkable turn of events just months after the worst attack on the Capitol in more than 200 years.

The bill as passed by the House would set up a bipartisan panel to investigate what happened when hundreds of former President Donald Trump’s supporters violently broke into the Capitol and interrupted the certification of President Joe Biden’s win.

A small number of Republicans, including Utah Sen. Mitt Romney and Alaska Sen. Lisa Murkowski, have said they expect to back the House-passed bill. Others, including Maine Sen. Susan Collins, have proposed tweaks to the bill to try and attract more votes. But the effort has so far failed to yield additional support.

The talks come as Republicans have struggled over whether to support the bill — and with how to respond to the insurrection in general as many in their party have remained loyal to Trump. The former president told his supporters the morning of Jan. 6 to “fight like hell” to overturn his defeat and has repeatedly said the election was stolen, even though his claims have been refuted by courts and election officials across the country.

Most Republicans are expected to follow the lead of Senate Republican Leader Mitch McConnell, who put the issue in stark political terms Tuesday after meeting with his caucus. McConnell said that Democrats pushing the commission would like to litigate Trump’s actions and “continue to debate things that have been done in the past,” and that they should move to block it.

Collins has said she is working with other senators to try to find a compromise, and Sen. Joe Manchin, D-West Virginia, has been part of that effort, according to two people familiar with the informal talks. The people spoke on condition of anonymity to discuss the private negotiations.

Collins’ amendment, released by her office Wednesday afternoon, confirmed changes that she advocated for earlier this week. It would require the Democratic-appointed chair and the Republican vice chair to “jointly appoint” staff, changing House language that only required the chair to consult with the vice chair.

It would also terminate the commission 30 days after a final report is issued, instead of 60 days, an effort to avoid their work spilling into the election year. Both the House version and Collins’ amendment would require the final report to be issued by Dec. 31, 2021.

“I want to see a commission, we need a commission, there are a lot of unanswered questions,” Collins said Wednesday. “I am working very hard to secure Republican votes.”

Still, most Republicans have held fast to their opposition. North Carolina Sen. Thom Tillis said that he had received text of the proposal from Collins, but that he was still “unlikely” to support the bill. He said he believes the year-end deadline is unrealistic.

Republicans have also pointed to a bipartisan Senate report that is expected to be released next month, saying it will be sufficient to fix security problems in the Capitol. The report by the Senate Rules Committee and the Senate Homeland and Governmental Affairs Committee is expected to focus on the mistakes made by law enforcement and the security command at the Capitol.

On Wednesday, the mother of Capitol Police officer Brian Sicknick said she would meet with lawmakers ahead of the vote to try to convince them to act. Sicknick collapsed immediately after engaging with the rioters and died the next day.

“Putting politics aside, wouldn’t they want to know the truth of what happened on January 6?” Gladys Sicknick said in a statement.

Story by Mary Clare Jalonick. Bangor Daily News writer Michael Shepherd and Associated Press writers Alan Fram, Colleen Long and Lisa Mascaro contributed to this report.