WASHINGTON — In blocking the formation of an independent commission to investigate the Jan. 6 Capitol riot, Republicans in Congress have all but closed off the possibility of a full and impartial accounting for one of the most serious assaults on American democracy in history, leaving unanswered critical questions with broad implications for politics, security and public trust.
Fearing political damage from any sustained scrutiny of the attack, Republicans united in large numbers against the inquiry, moving to shift an unwelcome spotlight away from former President Donald J. Trump, his election lies that fueled the attack, and the complicity of many G.O.P. lawmakers in amplifying his false claims of widespread voter fraud.
The result is that key details about a shocking act of domestic extremism against the United States government are likely to remain shrouded in mystery, and anything new that may be revealed about the assault at the Capitol will most likely be viewed through a partisan lens, with a substantial proportion of the country rejecting the reality of what transpired.
The public may never know precisely what Mr. Trump and members of his administration did or said as a throng of his supporters stormed the Capitol while Congress met to formalize President Biden’s victory, threatening the lives of lawmakers and the vice president. The full story may never be revealed of why security officials were so unprepared for the breach of the building, supposedly one of the most secure in the nation, despite ample warnings of potential violence. The extent of the role of Republican lawmakers closely allied with Mr. Trump in planning the Jan. 6 “Stop the Steal” rally that spiraled into a brutal onslaught may remain unexplored.
Despite its divisions, the United States formed fact-finding commissions after the attack of Pearl Harbor in 1941, the assassination of President John F. Kennedy in 1963 and the terrorist attacks of Sept. 11, 2001. The failure to do so in this case, said those involved in some of the inquiries, would further erode trust in the government, and deprive the public of the kinds of lessons that could prevent another such attack.
“After many of the national tragedies we’ve experienced over the last 50 or more years, the response was to have a bipartisan investigation that would lay out the facts in a way that would be definitive,” said Michael Chertoff, who served as homeland security secretary under President George W. Bush in the wake of the Sept. 11 attacks. “It builds trust. It shows the public at a time of crisis, we can all come together and put the good of the country ahead of partisan interests.”
Mr. Chertoff and three other former homeland security secretaries who served presidents of both parties had lobbied Republicans to support the creation of a Jan. 6 commission, saying the nation needed a better understanding of “how the violent insurrection at the Capitol came together to ensure the peaceful transfer of power in our country is never so threatened again.”
“We need to get a definitive explanation of what actually happened,” Mr. Chertoff said in an interview after the vote.
Even as the Justice Department moves to prosecute the rioters, congressional committees hold hearings and inspectors general examine their agencies’ responses to the attack, there is no outside group of experts charged with getting to the bottom of the myriad failings that led to the deadliest assault on the Capitol since the War of 1812.
What has been uncovered about the attack has only raised more questions:
Why did it take hours for the D.C. National Guard to receive approval to deploy to the Capitol to fight off the mob? Maj. Gen. William J. Walker, the D.C. National Guard commander at the time, has said he did not receive approval to mobilize troops until more than three hours after he had requested it. Defense Department and Capitol security officials have given conflicting statements about what happened.
What was Mr. Trump doing during the attack? He reportedly watched television as a mob stormed the Capitol, but later claimed that he had called in the National Guard, despite his defense secretary testifying that he never spoke to Mr. Trump that day. A Republican member of Congress said she was told that when Representative Kevin McCarthy of California, the House Republican leader, phoned Mr. Trump to ask him to call off the mob, he refused, siding with the rioters whom he said were evidently more upset about the election than Mr. McCarthy was.
What accounts for the lax precautions taken as right-wing extremists and militias openly planned to converge and wreak havoc on the Capitol that dark day? Leaders with the Capitol Police instructed officers to not to use their most forceful crowd control techniques and missed concerning intelligence reports. Security officials reportedly feared the “optics” of sending the National Guard to face off against supporters of Mr. Trump.
How much coordination was there among extremist groups, and to what extent were members of Congress involved in the planning of the rally that preceded the violence? An organizer of the “Stop the Steal” rally said three members of Congress “schemed up” the event with him, though two of the three have denied that claim.
Some on the right who support creating a commission have put forward their own questions, such as demanding more information about the shooting death of a protester, Ashli Babbitt, who was killed by a Capitol Police officer as she tried to force her way into a lobby just off the House floor where lawmakers were taking cover.
And perhaps most importantly, how can the country prevent another similar scenario from happening again?
For the United States, which holds itself out as a beacon of democracy, the rule of law and transparency, the death of the commission has also raised a more fundamental question: What happens when one political party effectively squelches any effort to look inward to assess government failings that have shaken the public’s faith in the nation’s institutions?
“This was not just a random event; it was existential in nature,” said Lee H. Hamilton, a former Democratic congressman from Indiana who was vice chairman of the 9/11 commission. “How in the world could this happen in this country? It was unbelievable that this far along in a democracy, we could have this kind of an event occur. It needs exploration.”
Many Republicans in Congress, whose leaders initially supported the idea of an independent commission, have spent the months since the assault trying to rewrite its history and downplay its severity. Their efforts appear to be working; a recent Quinnipiac Poll found that while 55 percent of Americans said they viewed what happened on Jan. 6 as an attack on democracy that should never be forgotten, nearly three-quarters of Republicans said that too much was being made of it and it was time to move on.
Senator Mitch McConnell, Republican of Kentucky and the minority leader, argued in advance of the vote that there was “no new fact about that day we need the Democrats’ extraneous commission to uncover.”
Mr. Hamilton said when he heard that, he thought to himself, “How does he know that?”
In the absence of a bipartisan commission, Democratic congressional leaders could create a select committee to investigate the attack, one with a broad mandate and subpoena power. Mr. Biden could also appoint a commission of his own, as some past presidents have done after national tragedies.
Alvin S. Felzenberg, a top aide and spokesman for the commission that investigated the Sept. 11 attacks, said there was a chance that such an inquiry could address some pressing questions, citing the Truman Committee that examined war profiteering in the 1940s and the Ervin committee that investigated Watergate in the 1970s. But an independent commission would have benefited from the full-time attention of the investigators, he argued, and its conclusions would have been more likely to be trusted by the public.
“Sitting members of Congress are pulled away from their work to address ongoing business before Congress,” Mr. Felzenberg said. “They also are starting to think about the next election. The 9/11 Commission and staff tended to nothing other than to their charge, spelled out in legislation.”
Former Gov. Bill Weld of Massachusetts, who worked as a lawyer on the Watergate inquiry, said the country was being denied “closure” by Republicans’ refusal to embrace a Jan. 6 commission. He said a select committee investigation would need buy-in from both parties to be seen as legitimate.
“It would have to be bipartisan to be credible,” Mr. Weld said. “Everybody’s got to be on board for it.”
Many of the Republicans who opposed the commission conceded there were a litany of unanswered questions about the events of Jan. 6, but they argued the independent commission’s work would be duplicative of several continuing investigations.
Senator Mike Lee, Republican of Utah, said he favored inquires by Senate committees to explore “the many legitimate questions that remain to be answered” over what he viewed as a “political” commission.
Unlike the work being done by Senate committees, which are focused on security breakdowns, the commission — a panel of 10 experts, evenly split between Republican and Democratic appointees — would have had the broad authority to connect various threads of inquiry and compile a single comprehensive record for American history, as the 9/11 Commission did after those terrorist attacks.
Mr. Bush and Vice President Dick Cheney both testified before that commission, and supporters of a Jan. 6 commission were hopeful it could force testimony from Mr. Trump or at least those who spoke with him as the violence escalated, such as Mr. McCarthy.
“Is it going to reveal anything more than we would have gotten otherwise?” Senator Lisa Murkowski, Republican of Alaska, said before breaking with her party to vote to move ahead with the commission. “I don’t know and I guess now we’ll never know. But isn’t that part of the problem — that we’ll never know?”
The Justice Department’s investigation into Jan. 6 is, at this point, one of the largest criminal inquiries in U.S. history, with more than 400 defendants. In court filings, several of the defendants have said that they were merely following the orders of Mr. Trump, saying the former president urged them on to storm the Capitol. But none of those prosecutions are looking into security or governance breakdowns.
“We need to figure out who knew what when,” said Lt. Gen. Russel L. Honoré, who was chosen by Speaker Nancy Pelosi to lead a security review of the Capitol in the aftermath of the riot, adding that an independent commission was still badly needed. “Our government did not work that day.”
Republican leaders, he said, had killed the commission because it “might make them look bad in the next election.”
“That’s a damn crying shame,” General Honoré said in an interview. “What a damning message this sends to the Capitol Police.”
About 140 officers were injured in the attack on the Capitol. Many were smashed in the head with baseball bats, flag poles and pipes. Officer Brian D. Sicknick, who was allegedly sprayed with bear spray, collapsed and died afterward, and two officers who clashed with the mob later took their own lives.
Officer Sicknick’s mother, Gladys, and a small group of officers who survived the assault made a last-ditch effort to lobby for an independent investigation, visiting Republican senators’ offices this week to urge them to drop their opposition.
“If Jan. 6 didn’t happen, Brian would still be here,” Harry Dunn, a Black Capitol Police officer who fought the mob as they hurled racial slurs at him, told reporters between visits.
But ultimately, Republicans rallied behind Mr. McConnell, who told his colleagues that Democrats would try to use the commission to hurt their party in the 2022 midterm elections, and urged them to block it.
Alan Feuer and Katie Benner contributed reporting.