The president of the United States summoned his supporters to Washington, D.C., today, and then stood in front of the White House and lied to them, insisting that he had won the election and that extraordinary measures were necessary to vindicate his win. They took his message to heart, marching up the National Mall toward Capitol Hill. Breaking through barricades and police lines, Confederate battle flags dotting the crowd, the insurrectionists seized control of the United States Capitol, putting Congress to flight.

Four years ago, Donald Trump swore to faithfully execute the office of president of the United States and, to the best of his ability, to preserve, protect, and defend the Constitution of the United States. He lost little time in breaking that oath. On December 18, 2019, the House of Representatives reluctantly and belatedly performed its constitutional duty, impeaching the president for abusing his power and obstructing Congress. The Senate refused to similarly perform its own constitutional duty, declining to take up the charges in earnest and failing to muster the requisite two-thirds majority for removal. Only a single Republican, Senator Mitt Romney, acknowledged the obvious truth of the charges, voting to remove the president from office.

Trump has today broken his oath in even more spectacular fashion. The seeds sown by Republican obeisance and congressional quiescence have now yielded their bitter harvest. With his incitement of a direct assault on the people’s house, the president has forfeited his claim to finish his term. The House must again impeach him, and the Senate must vote to remove him. And as it does so, it must bar him from ever again serving in public office.

As the sun set on Washington on Friday, February 21, 1868, the nation braced itself for a second Civil War. In open defiance of Congress, President Andrew Johnson had dismissed his secretary of war, Edwin Stanton, and appointed General Lorenzo Thomas in his stead. Stanton stood his ground. He posted an armed guard outside the War Department. The Grand Army of the Republic, the Union veterans’ group, mobilized battalions of members in civilian dress to patrol the city; its commander began planning a secret, nationwide mobilization. “If violence is used to eject Mr. Stanton, one hundred thousand men are ready to come to Washington to put him back,” newspapers reported. Union veterans, the San Francisco Chronicle promised, “who whipped the flower of the Confederacy, before they had kissed the dust in the humiliation of defeat,” stood ready to renew the fight.

Yet Stanton turned not to violence, but to law. First, he appealed to the Senate, which on Friday night approved a resolution backing his position, 29–6. Then, he swore out an affidavit for Thomas’s arrest; early Saturday morning, constables dragged Thomas into court, where he was released on $5,000 bail. But the real drama was in the House of Representatives. At 2 p.m. on Saturday afternoon, its Reconstruction Committee initiated impeachment proceedings against Johnson on the floor of the House.

Meanwhile, fearing a coup, Johnson summoned the general commanding the forces around Washington to the White House, asking him to swap the units of U.S. Colored Troops deployed in the capital for (presumably more sympathetic) white soldiers. The garrison commander refused, telling Johnson that Congress had stripped him of the right to directly issue orders; all commands had to be passed through General Ulysses S. Grant, who was still taking his instructions from Stanton. The president had lost control of the Army. Wild rumors swirled. Had the governor of Maryland offered Johnson the use of his state’s militia? Were 100,000 volunteers on offer from Missouri? Was Johnson asserting control of the War Office in order to use the arsenal of weapons in the capital to arm his supporters?

Johnson’s defenders in the House argued that impeachment—or worse, conviction—posed the clearest threat to the constitutional order. It would be “the overthrow and destruction of our form of government,” thundered the New York Democrat James Brooks, presenting impeachment as an attempt to “depose the president of the United States.” Democrats insisted the matter was best left to the courts, or the consequences could be dire. “We are evidently on the eve of a revolution that may, should appeal be taken to arms, be more bloody than that inaugurated by the firing on Fort Sumter,” warned the staunchly Democratic Boston Post.

Nonsense, replied John Bingham of Ohio, the principal author of the Fourteenth Amendment. The question was whether the president would be allowed “to set himself above the Constitution and above the laws.” The Constitution gave the House, and the House alone, the responsibility for determining whether the president had committed an impeachable offense; the question could not be delegated to the courts. Impeachment, Bingham insisted, was not a threat to public order, but rather, the constitutional means of restoring it. The debate continued in that vein—Democrats insisting that impeachment threatened violence, and Republicans, that it would avert it. On Monday, the House put the question to the test. For the first time in American history, it voted to impeach a president of the United States.

And with that, the fever broke. “Affairs to Be Settled Without Bloodshed,” the Louisville Daily Courier sighed with relief. “To-day but for Congress there would be war,” the Philadelphia Post applauded. Instead of raising armies and firing cannons, the parties hired lawyers and filed motions. Impeachment took the fight off the streets and into the halls of Congress, channeling partisan passion into parliamentary procedures.

This has always been the greatest value of impeachment. It is most often debated in legalistic terms, as a question of evidence and constitutional interpretation. Views of particular efforts at impeachment are usually reasoned backward from the preferred result, along partisan lines. But that is too narrow a view. Impeachment is the constitutional mechanism for considering whether a president is subverting the rule of law, or abusing his power, or pursuing his own self-interest at the expense of the general welfare—in short, whether his continued tenure in office poses a threat to the republic.

That was what the American people were really debating in 1868. It is what they debated again in 1974, during the presidency of Richard Nixon. And it is the question they confront again today.

We have seen today the terrible cost of Congress’s abdication of its constitutional responsibilities, the chaos and the violence that come when it refuses to hold the chief executive to account for breaking his oath and violating his constitutional responsibilities. Trump poses a danger each day he remains in office, wrapped in solipsistic self-pity, heedless of the damage he inflicts on his supporters, and on the country.

Congress must now act, not just to remove Trump—but to ensure that no president ever risks behaving in this way again. Impeachment is the constitutional mechanism for holding a president accountable, a defiant emphasis upon the rule of law in the face of mob violence, a reassertion of the primacy of American institutions over the rule of passions.

Trump has authored his own indictment, and the evidence of his lips condemns him. If senators could not see it a year ago, when the violence he incited was visited upon the most vulnerable, perhaps they have seen it today, as the violence arrived at their doorstep.

The president must be impeached.