WASHINGTON — Speaker Nancy Pelosi on Sunday appointed Representative Adam Kinzinger to the special committee investigating the Jan. 6 riot at the Capitol, adding a second Republican who is a forceful critic of former President Donald J. Trump to the panel.
The move, which bolsters the committee’s bipartisan credentials, came after Ms. Pelosi rejected two Republicans who are among Mr. Trump’s most vociferous defenders in Congress from joining, saying their conduct suggested they could not be trusted to participate.
Mr. Kinzinger, a six-term congressman from Illinois who has drawn censure from his own party for disavowing Mr. Trump and the conspiracy theories the former president perpetuated, said in a statement that he had accepted the post.
“While this is not the position I expected to be in or sought out, when duty calls, I will always answer,” said Mr. Kinzinger, one of 10 House Republicans who voted to impeach Mr. Trump. “This moment requires a serious, cleareyed, nonpartisan approach. We are duty bound to conduct a full investigation on the worst attack on the Capitol since 1814 and to make sure it can never happen again.”
Ms. Pelosi, who has final say over the committee’s membership, has already given one of the eight seats normally reserved for the majority party to Representative Liz Cheney, Republican of Wyoming. Ms. Cheney was ousted from House leadership in May for criticizing Mr. Trump and his actions before and during the riot.
About 140 police officers were injured on Jan. 6 as Trump loyalists stormed the Capitol, where Congress was meeting to formalize President Biden’s election, chanting “Hang Mike Pence,” stalking the halls for Ms. Pelosi and forcing lawmakers to evacuate their chambers.
Ms. Pelosi began seriously considering unilaterally appointing Mr. Kinzinger last week after she blocked Representatives Jim Banks of Indiana and Jim Jordan of Ohio. Both had amplified Mr. Trump’s false claims of election fraud, joined their party’s efforts to challenge Mr. Biden’s victory on Jan. 6 and made statements that undermined the select committee’s work and mission.
Ms. Pelosi, however, said she welcomed the three other Republicans whom Representative Kevin McCarthy of California had nominated to join the panel.
“We have to ignore the antics of those who do not want to find the truth,” she said Sunday on ABC’s “This Week,” reiterating her rationale for barring Mr. Banks and Mr. Jordan.
Her decision to reject the pair drew an angry response from Mr. McCarthy, the minority leader, who announced that all his picks would boycott the panel. He has described Ms. Pelosi’s intervention as confirmation that the investigation was nothing more than a political exercise to hurt the G.O.P.
“Speaker Pelosi’s rejection of the Republican nominees to serve on the committee and self-appointment of members who share her preconceived narrative will not yield a serious investigation,” he said in a statement on Sunday.
On “Fox News Sunday,” Mr. Banks, who arranged a recent trip to join Mr. Trump at the southwestern border, blamed Ms. Pelosi for the security breakdowns at the Capitol during the breach by the pro-Trump mob. He claimed, without evidence, that he was rejected from the committee as part of a cover-up.
“Why was there a systemic breakdown of security on Jan. 6?” Mr. Banks asked. “At the end of the day, she is ultimately responsible for the breakdown of security at the Capitol that happened on Jan. 6.”
Congressional leaders hire the law enforcement personnel responsible for Capitol security, but are typically not involved in day-to-day decisions about security protocols.
Security at the Capitol is controlled by the Capitol Police Board, which includes the House and Senate sergeants-at-arms and the architect of the Capitol. At the time of the attack, the House sergeant-at-arms, Paul D. Irving, had been on the job since 2012, when he was hired under Speaker John A. Boehner, Republican of Ohio. The Senate sergeant-at-arms at the time, Michael Stenger, was hired in 2018 when Senator Mitch McConnell, Republican of Kentucky, led the chamber.
Both Mr. Irving and Mr. Stenger, along with the chief of the Capitol Police at the time, Steven A. Sund, resigned under pressure after the riot.
Asked about Mr. Kinzinger’s potential selection on Sunday, Mr. Banks pointed to his colleague’s unsparing criticism of Mr. Trump: “It’s clear that Pelosi only wants members on this committee who will stick to her talking points and stick to her narrative.”
Mr. Kinzinger has urged his fellow Republicans to reject Mr. Trump’s lie of a stolen election and his brand of grievance-based politics, betting his political career that his party’s future lies in repudiating the former president.
“For months, lies and conspiracy theories have been spread, threatening our self-governance,” Mr. Kinzinger said on Sunday.
In her statement appointing Mr. Kinzinger to the panel, Ms. Pelosi emphasized his military service as an Air Force veteran and lieutenant colonel in the Air National Guard.
“He brings great patriotism to the committee’s mission: to find the facts and protect our democracy,” she said.
There will now be nine members of the committee seated when the panel has its first hearing on Tuesday. The investigation is set to begin with the testimony of police officers who helped fight off the mob attack.
Among them are Officer Harry Dunn; Aquilino Gonell, a sergeant; Michael Fanone, who has lobbied Republicans to support an investigation; and Daniel Hodges, who was crushed in a door during the rampage.