The House is poised to launch a new investigation of the Jan. 6 Capitol insurrection on Wednesday with the expected approval of a 13-person select 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 members.

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 select panel “is likely to pursue a partisan agenda” in investigating the siege by former President Donald Trump’s supporters. Scalise and McCarthy have so far declined to say whether Republicans will even participate.

Pelosi is moving to form the select 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. Republicans ready to move on from the insurrection — and Trump’s role in it — argued against that as well, claiming it would be duplicative and partisan.

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.

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, Democrats, and even some of his fellow Republicans.

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.

Many Republicans have expressed concerns about a partisan probe since the majority of Democrats are likely to investigate Trump’s role in the siege and the right-wing 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.

Seven people died during and after the rioting, including Babbitt and three other Trump supporters who suffered medical emergencies. Two police officers died by suicide in the days that followed, and a third officer, Capitol Police Officer Brian Sicknick, collapsed and later died after engaging with the protesters. A medical examiner later determined he died of natural causes.