Saturday’s 57-to-43 vote brought an end to Congress’s formal effort to hold former president Donald Trump accountable for the Jan. 6 insurrection at the Capitol. But that traumatic moment for the country will not quickly fade, nor should it, not after an attack on the symbol of democracy and democracy itself.

The Senate vote left multiple questions still to be answered, including some that the president’s legal team deflected during the trial. Chief among them: Exactly what did Trump know as the attacks were unfolding, and why he didn’t he do anything to protect Vice President Mike Pence or order immediate reinforcements to the beleaguered law enforcement officers at the Capitol? Trump could yet face judgment in court, whether criminal or civil, but the full story of what happened and how it happened remains untold.

One vehicle for fact finding that could lead to protecting the Capitol, those who work there and the democratic institutions they are sworn to defend is the kind of commission that Tom Kean, the former Republican governor of New Jersey, and Lee Hamilton, the former Democratic House member from Indiana, headed after 9/11 and now are advocating to investigate the Jan. 6 events.

On Friday, Kean and Hamilton sent a letter to President Biden and to the bipartisan leaders in the House and Senate urging the establishment of a commission that would be both independent and bipartisan. In a time of partisanship and, among most Republicans tribal loyalty to Trump, it will be a challenge to assemble a group that meets those criteria, but the two leaders say it is, nonetheless, essential to try.

In the letter, the two wrote, “The shocking and tragic assault of Jan. 6th on the U.S. Capitol requires thorough investigation, to ensure that the American people learn the truth of what happened that day. An investigation should establish a single narrative and set of facts to identify how the Capitol was left vulnerable, as well as corrective actions to make the institution safe again.”

Neither Kean nor Hamilton sought to make a direct comparison with the events of Sept. 11, 2001, and those of Jan. 6. But as Kean put it in an interview: The Capitol attack “was a wound to democracy itself. . . . If the people we elect cannot be safe when they’re trying to do their work, then the country’s in trouble and will remain in trouble, and we’ve got to therefore get to the bottom of it.”

House Speaker Nancy Pelosi (D-Calif.) already has raised the idea of creating such a commission, as have some other members of Congress. Kean and Hamilton said that each had received a call from the speaker on Friday, following up on their letter and plumbing their expertise. But is there the will in Congress as a whole to go ahead with such an investigation after the Senate trial?

In their letter, sent under the auspices of the Bipartisan Policy Center, Kean and Hamilton acknowledged that it is the role and responsibility of Congress to decide whether to establish such a commission and how to structure it. As such, they did not mention the name of Trump or note that it was his followers who invaded the Capitol after having been called to Washington by the former president after being fed repeated lies for weeks about a stolen election. Their focus is on shoring up the institution of Congress, in terms of security and capacity to do its job.

But there is no question that any such commission would inevitably be confronted by the causes of this act of domestic terrorism, of insurrection, and presumably how Trump empowered those who put the lives of lawmakers and Capitol Hill staff in danger.

Some lawmakers said former president Donald Trump’s political future was over on Feb. 14, one day after the Senate acquitted him for the second time in a year. (JM Rieger/The Washington Post)

In an interview, neither Kean nor Hamilton directly addressed whether a new commission examining what happened on Jan. 6 could avoid dealing with the former president’s role. Instead, they said the key to a successful investigation, particularly in these fraught times, begins with the selection the right people, both as commission members and as the commission staff, to lead it.

“[You] want to avoid the trap of partisanship,” Hamilton said. “You want to make sure you appoint high-quality people who have the good of the country at heart, are serious about it and honest about it, people with integrity who will examine the facts and not be swayed by ideology or partisanship.”

Yet both acknowledged that any commission appointed to investigate the attacks on the Capitol would be doing so in a far different environment than existed when they did their work. The attacks on Sept. 11, 2001, rallied the country in unity against international terrorism. Not so the attacks on the Capitol, though deplored by vast majorities of the country.

“I think it’s more difficult,” Kean said, “not only because of the former president but because the time is different. . . . It’s very hard to get people to talk about politics in a way that gives decent respect to points of view on all sides. . . . That doesn’t mean you can’t do it [establish a commission]. I mean, you still have to do it.”

Hamilton added, “The time is one of very acute, intense partisanship and that makes any investigation more difficult. But they [commission members and staff] simply have to shut that out as much as they possibly can.”

The first goal of any such commission, they said, is to establish the facts of what happened that day, to set out a thorough timeline of events based on exhaustive investigation of all the evidence. “Once you get the report right, the recommendations come spilling right out of the report,” Kean said. “Every single recommendation we made was based on a fact we found in our report.”

To be able to establish facts and a timeline, Hamilton and Kean wrote, a commission should have wide-ranging “authority, through subpoena power, to interview witnesses and review all documents, videos, communications and computer media it requires.”

The two leaders of the 9/11 commission know from their own experience the many obstacles any future commission would face, particularly those of time and resources. Both said attempting to set a deadline for completion of a report at the start of the work would be a mistake. “You take the time you need and if you don’t have that time available, and if they’re not going to give you the time you think is necessary, then just don’t do it,” Hamilton said.

“We found out pretty early in our case we needed more time and that we didn’t have enough money,” Kean said. The two had to plead with Congress for ample resources and the time to complete their work. “If they had not [agreed], it would not have been the quality report it was,” he added.

If the 9/11 commission is a guide, Congress would appoint commission members and the president would name the chair. That commission, which became a model for such bodies, eventually included a staff of roughly 70 people and the work took a year and a half to complete.

Beyond examining the attacks on the Capitol and why the complex was left as vulnerable as it turned out to be, Kean and Hamilton suggested another role for a new commission: To examine ways to strengthen Congress itself, through reforms that would build public trust and that would give Congress greater capacity to address the country’s problems. That dual mandate could significantly expand and complicate the scope of a new commission.

Inevitably there will be various calls for investigations of what happened on Jan. 6. The risk is that they become partisan exercises. What Kean and Hamilton recognize is that only a commission shorn as much as possible of partisanship and ideological overtones can hope to produce the kind of accounting of events that will be needed to protect the Capitol and those who work there in the future.

The second impeachment trial of the former president, which turned largely on partisan loyalty to Trump among Republicans, showed how challenging it would be to replicate the work of the commission that Kean and Hamilton so ably led but also why it might be badly needed.

“Our country has been wounded,” Kean and Hamilton said in their letter to the leaders. “A full accounting of the events of Jan. 6th and the identification of measures to strengthen the Congress can help our country heal.”