The Jan. 6 Committee Carries History’s Weight Its members need to nail down what happened on the Capitol—including in their colleagues’ offices.

“It happened, move on.” “It wasn’t so bad.” “It was just a protest that got out of hand.” A lot of the rioters were screwballs in antlers—crazy uncles, unhappy sons. They didn’t even have a plan. They didn’t know what they were going to do in there. They just ran around and screamed. “Hang Mike Pence. ” You get the distinct impression from the videos that they were extremely relieved they couldn’t find Mr. Pence, or anyone else.

These are aspects of the events of 1/6/21, but they aren’t anywhere near the most important ones.

There are three reasons we have to learn everything we can about what happened that day, and they are the reasons the House Select Committee to Investigate the Jan. 6 Attack on the United States Capitol, which held its first public hearing this week, deserves the support of both parties.

Rep. Liz Cheney embraces a police officer set to testify at the first congressional hearing on the events of Jan. 6
Rep. Liz Cheney embraces a police officer set to testify at the first congressional hearing on the events of Jan. 6

One is that the central intent of the riot was to halt, unlawfully and through violence, a constitutionally mandated activity: the counting of the physical Electoral College ballots that would yield the final, formal result of the 2020 presidential election. Those paper ballots, transported to Washington by each of the 50 states, rested inside wooden boxes secured by thick leather straps and placed on the floor of the U.S. Senate. Their counting is an expression, but also a practical requirement, of the peaceful transfer of presidential power. Their counting had never been stopped before, even in America’s wild wilderness beginnings.

If we have a future in which such attempts become commonplace, everything will fall apart: No future presidential outcome will be assumed to be settled, no transfer of power peaceful. That would be a disaster.

Something else almost as important: The melee, the whole crisis of 1/6, made America look unstable, hollow, all facade. In a predatory world such appearances are dangerous. What happened that day knocked us down a few pegs, disheartening our international friends and exciting our foes. (Imagine what those cool operators in Beijing thought as they watched the videos. These are the people with whom we’ll spend the 21st century in epic struggle? OK!)

These are the reasons what happened on 1/6 can’t be allowed to become normal. One way to discourage that is to see that all involved pay a steep practical and reputational price—public exposure, shame and, when a crime can be proved, prison time. To determine who deserves this requires investigation.

Indignation is a form of loyalty. You protect the things you love.

The committee hearing this week focused on public testimony from four police officers who described what 1/6 was really like—not just a lark by guys in antlers but a day of considerable blood lust. They testified that they were physically and verbally assaulted, targeted by the mob, kicked, punched, crushed and sprayed with chemicals.

Rep. Liz Cheney asked: Was it a “loving crowd,” as Donald Trump has described it? “I’m still recovering from those hugs and kisses that day,” Capitol Police Sgt. Aquilino Gonell responded dryly. He characterized the day as “a medieval battle.”

The committee will have a chance to create a formal record and secure details that amplify and supplement what we think we already know. Some of it may be surprising and some shocking.

Members of the Republican leadership are making a huge error in how they are responding to the committee. They misunderstand their own position. They should be quietly trying to push away from the disaster by leaving it on Mr. Trump and his White House, not their party. They should have taken part in the committee investigation, defended those who entered the Capitol but did no harm and truly thought their presence was legal—the president, some have said, told them to do it—while letting the evidence against Mr. Trump pile up.

Instead they’ve played down what happened and dismissed the committee as a partisan effort. They have put their party on the wrong side of reality. When House Republican Leader Kevin McCarthy called the two Republicans on the panel, Ms. Cheney and Rep. Adam Kinzinger, “Pelosi Republicans,” he looked unserious and stupid. He breathed more oxygen into crazytown theories of a stolen election, and again propped up Mr. Trump, whose support in the party is broad, true, but also shallow. Trump supporters are loyal to him and defend him, but when you talk to them you sense their passions are moving on. The candidate he endorsed in a special congressional runoff election in Texas just lost by a resounding six points.

The reality of Donald Trump torments a lot of the GOP leadership, and yet they constantly revive him. They set their fortunes with his when the physics of politics dictates one thing: Out of power, removed from the presidency and denied social media, this is a balloon losing air, not gaining it.

Republican leaders think they’re playing to his base, and they forgive this in themselves by telling themselves stories about how he really may have won the election. They aren’t loyal, they have Stockholm syndrome: They’ve come to identify with the guy who took them hostage and hope the cops don’t hurt him.

The committee should spend the next few months doing everything it can to get the story. More important than the timing of future hearings this fall and winter is what can be gotten that is deep and new—real information that has never been heard before. Members should focus on what drove this thing, who quietly encouraged it. The collapse of Capitol security has already been done. More interesting now: Were members of Congress in communication with the rioters? Did any advise or coordinate with them before 1/6? What did they say to the White House by phone and text on 1/6?

There’s an important roadmap in the books coming out about Mr. Trump’s final days in the White House. Everyone around the former president seems to be talking, usually not for attribution. Most of what they say is not complimentary. Much that has already come out is valuable, a contribution to the record, but it all lacks the true heft of history because it reflects the limits of journalism. Reporters don’t have subpoena power. They can’t make their sources speak under oath.

The committee can. Democrats in recent investigations have been slow to use the subpoena. They say this time they will. To get the story they’ll have to.

I hope they get at least one of their colleagues on the record on this: Some representatives who later insisted the rioters were peaceful patriots, that it was all just another day with rowdy, happy tourists, accepted the protection of the police they now deride on 1/6. If the protesters were such gentle souls, the representatives could have confidently refused police protection, refused to hide in undisclosed locations, walked freely into the halls, and told their fellow Trump supporters that while their passion was understandable they were breaking the law. “March with me to the exits. We will move our questions about the election forward in the courts, but lawfully.”

Why didn’t they? Because they were afraid of the people they now excuse? They were scared little rabbits who finally knew what they’d unleashed.

Nail this story down. Nail everyone involved. Then, and only then, move on.