The answer was settled on the battlefield, but it was ratified through the 14th Amendment, which defined who is a citizen of the United States and established that the “privileges or immunities” of same supersede any state laws that might abridge them. From now on, there would be no ambiguity: Under the Constitution, the people of the United States are sovereign, and this sovereignty supersedes the sovereignty of the people of the individual states whenever the privileges and immunities of the former are in conflict with the will of the latter.
Section 3 of that amendment was similarly enacted in order to secure federal supremacy. Rebel officers might well have retained strong popular support in the former Confederate states, but Section 3 prevented the rebellion from being continued by electoral means. The people of South Carolina might prefer to be represented by former rebels, but the people of the United States, whose sovereignty trumps South Carolina’s, forbid it.
Whose sovereignty, though, trumps the people as a whole?
Donald Trump is the overwhelming favorite to win the Republican nomination for president and has a close to even-odds chance of winning the general election. That would seem to have no bearing on his eligibility to run. If a majority of the country wanted Barack Obama or Arnold Schwarzenegger or Selena Gomez to be president, it would be out of luck. The Constitution renders them ineligible: Mr. Obama has already been elected twice, Mr. Schwarzenegger was not born a U.S. citizen and Ms. Gomez is under 35 years old.
For that very reason, though, those individuals aren’t likely to run — and if they did try to run, their ineligibility would be manifest, recognized by everyone. Similarly, former Confederate officers and officials, by serving in the Confederacy, had explicitly declared themselves insurrectionists. Congress passed a broad amnesty in 1872 to lift the penalties associated with the involvement of most in insurrection, including that imposed by Section 3 of the 14th Amendment; some individuals not covered by the amnesty petitioned successfully for the restoration of their civil rights, and in other cases the prohibition was simply not enforced. But the essential fact of participation in the insurrection was not in dispute.
The situation with Mr. Trump could not be more different. An overwhelming majority of his party, and apparently about half of the country as a whole, considers him to be eligible to be president again. Moreover, these voters believe this even though, as President Biden said recently, “we saw with our own eyes” what happened on Jan. 6.