The political wisdom of using a constitutional provision to bar Trump from the presidential race, and thereby deny voters a free choice as to whether he should return to the White House, is debatable. So is the question of whether Section 3 is “self-enacting” in his case. Is he disqualified because he did what he did, or does he need to be convicted?

All this aside, the history suggests that the framers of the 14th Amendment had just these types of dangers in mind. They meant to bar from office anyone who attempted to subvert the Constitution and end our system of government. To understand why Trump might be constitutionally ineligible to serve, it’s critical to review the origins of Section 3.

In the immediate aftermath of the Civil War, Republicans in Washington faced a double conundrum.

They had vanquished the Confederacy and compelled Southern states to remain in the Union. But victory could prove to be a Trojan horse. With Southern states restored to their former relationship with the federal government, they might soon send representatives and senators to Congress, where in combination with their Northern Democratic allies, they could regain control of the federal government, effectively winding the clock back to 1860. Worse still, the abolition of slavery rendered the old three-fifths compromise moot. Southern representation in Congress and in the electoral college would increase, even though Southern states signaled early on their intention to keep Black residents in a state of permanent political, social and economic subjugation through the enactment in the summer and fall of 1865 of “Black Codes” that severely restricted the rights of free Black people.

Worse still, Abraham Lincoln’s assassination left the presidency to Andrew Johnson — like other War Democrats, he supported the Union effort and embraced emancipation as a war measure and aim — who now hoped to effect a swift restoration of the old Union (albeit without slavery). Between the spring and December, when the new Congress would be sworn in, Johnson took steps to recognize new, Democratic-controlled governments — first in North Carolina and then throughout the South — and issued a sweeping amnesty proclamation that pardoned (and thus affirmed the U.S. citizenship) of all former Confederates except 14 categories of people, most of whom were large landowners with property in excess of $20,000 (a lofty sum at the time) or high officials of the Confederacy. Even then, Johnson began handing out dozens of presidential pardons to such people throughout the fall, against the advice of moderate Republicans who were otherwise inclined to trust him.

These events alarmed and appalled most Republicans, and especially radicals like Rep. Thaddeus Stevens of Pennsylvania, the grim-faced, irascible “Dictator of the House.” With his piercing gaze and ruthless authority, Stevens, who served as chair of the Ways and Means Committee during the war, was also the unspoken floor leader for the House Republican caucus. He maintained tight control over the chamber, even as he advocated policies that were far more radical than his caucus in his desire to punish the South and impose Black political and economic equality. Stevens advanced the idea that the Southern states were “conquered territories,” their residents no longer citizens of the U.S. and certainly not entitled to govern themselves, let alone participate in the governance of the whole nation.