WASHINGTON (AP) — The House is poised to launch a new investigation of the Jan. 6 Capitol insurrection on Wednesday with expected approval of a special committee to probe the violent attack.

The panel would be led by Democrats, with House Speaker Nancy Pelosi appointing a chairperson and at least eight of the committee's 13 members. The resolution up for a vote gives Pelosi a possible say in the appointment of the other five members as well, directing that they will be named “after consultation” with House Republican leader Kevin McCarthy.

Most Republicans are expected to oppose the panel. In a memo to all House Republicans late Tuesday, No. 2 House Republican Steve Scalise urged his members to vote against the resolution, saying the committee “is likely to pursue a partisan agenda” in investigating the siege by former President Donald Trump’s supporters. Republicans want to move on from the insurrection — and Trump’s role — and Scalise and McCarthy have declined to say whether Republicans will even participate.

Pelosi moved to form the committee after Senate Republicans blocked the creation of a separate independent and bipartisan panel that would have been evenly split between the parties and modeled after a commission that investigated the 9/11 terrorist attacks.

The speaker has said that it was her preference to have an independent panel lead the inquiry, but that Congress could not wait any longer to begin a deeper look at the insurrection.

“It is clear that January 6th was not simply an attack on a building, but an attack on our very Democracy,” Pelosi said in a letter to colleagues Wednesday morning. “It is imperative that we seek the truth of what happened.”

The GOP role in the probe, and the appointments to the panel, could help determine whether the committee becomes a bipartisan effort or a tool of further division. Two Senate committees issued a bipartisan report with security recommendations earlier this month, but it did not examine the origins of the siege, leaving many unanswered questions about the events of the day.

McCarthy is facing pressure to take the investigation seriously from police officers who responded to the attack as well as from Democrats and even some of his fellow Republicans. Officers who responded that day, including Metropolitan Police Officers Michael Fanone and Daniel Hodges and Capitol Police Officer Harry Dunn were expected to attend the vote in the House Gallery, according to Pelosi's office.

Dozens of officers suffered injuries as Trump’s supporters pushed past them and broke into the building to interrupt the certification of President Joe Biden’s victory. Fanone has described being dragged down the Capitol steps by rioters who shocked him with a stun gun and beat him. Hodges was crushed between two doors. And Dunn has said that rioters yelled racial slurs and fought him in what resembled hand to hand combat as he held them back.

Also expected in the gallery were Gladys Sicknick and Sandra Garza, the mother and partner of Capitol Police Officer Brian Sicknick, who collapsed and later died after engaging with the protesters. He was sprayed with chemical irritants, but a medical examiner determined he died of natural causes.

Fanone and Dunn met with McCarthy on Friday and asked him to take the House investigation seriously. Fanone said he asked McCarthy for a commitment not to put “the wrong people” on the panel, a reference to those in the GOP who have downplayed the violence and defended the insurrectionists. He said McCarthy told him he would take his request seriously.

Sen. Mitt Romney, R-Utah, has also publicly pressured McCarthy. “I hope he appoints people who are seen as being credible,” he said Sunday on CNN.

Ohio Rep. Jim Jordan, a Trump ally, said it's possible Republicans will just choose not to be involved.

“I know I've got real concerns, I know he does, that this is all just political, and that this is impeachment three against President Trump," Jordan said.

Trump was twice impeached by the House and twice acquitted by the Senate, the second time for telling his supporters just before the insurrection to “fight like hell” to overturn his defeat to Biden.

Pelosi has not yet said who will lead the panel, but one possibility is House Homeland Security Committee Chair Bennie Thompson, D-Miss. Thompson said Tuesday that it would be an honor to serve as chair and that it's Pelosi's call if she wants to have a say on the Republican members.

“They had an opportunity to really engage,” Thompson said of Republicans who voted against the bipartisan commission. “And they didn't. So they can't now come back and say, ‘Oh, that’s not fair.'"

Many Republicans have expressed concerns about a partisan probe, since majority Democrats are likely to investigate Trump’s role in the siege and the groups that participated in it. Almost three dozen House Republicans voted last month for the legislation to create an independent commission, and seven Republicans in the Senate have also supported moving forward on that bill. But that was short of the 10 Senate Republicans who would be necessary to pass it.

Many Republicans have made clear that they want to move on from the Jan. 6 attack. But some have gone further, including Rep. Andrew Clyde of Georgia, who suggested that video of the rioters looked like a “tourist visit." Rep. Paul Gosar of Arizona insisted that a Trump supporter named Ashli Babbitt, who was shot and killed that day while trying to break into the House chamber, was “executed.” Others have defended rioters charged with federal crimes.

Seven people died during and after the rioting, including Babbitt and three other Trump supporters who suffered medical emergencies. In addition to Sicknick, two police officers died by suicide in the days that followed.

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Associated Press writers Lisa Mascaro, Kevin Freking and Padmananda Rama contributed to this report.