Law Professor Derek Muller has this essay, pointing out that just because a judicial determination is someday made that Donald Trump is ineligible to run for president in 2024 due to Section Three of the 14th amendment, it doesn’t follow that he will be kept off 2024 ballots.
Section Three of the 14th Amendment says, “No person shall…hold any office, civil or military, under the United States, or under any State, who, having previously taken an oath, as a member of Congress, or as an officer of the United States…to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same.”
Some scholars have been saying that former President Trump may therefore not be eligible to be president again. But Professor Muller points out that just because someone is ineligible to be president, it doesn’t follow that he or she won’t be allowed on the ballot. In 1892, the Prohibition Party nominee for vice-president, James B. Cranfill, was under age 35, but every state except South Dakota printed his name on government-printed ballots (except for the states that didn’t yet have government-printed ballots). Everyone knew that Cranfill was under-age. He and the Prohibition Party made no secret of his age. But he wasn’t barred from the ballot in any state on those grounds, because back then everyone understood that the true candidates in November are the candidates for presidential elector.
His name was not on the ballot in South Dakota because the entire Prohibition Party ticket was absent from the South Dakota ballot in 1892, because the state officers of the party were sympathetic to Republican nominee Benjamin Harrison, so they didn’t file the paperwork for the Prohibition nominees to be on the ballot.
If Trump is the Republican nominee in 2024, but he has been ruled ineligible under the 14th amendment, section 3, it would be the job of Congress in January to reject the electoral votes for Trump on the grounds that Trump is not eligible. Congress refused to count the electoral votes for Horace Greeley in 1872 on grounds that he was ineligible (because he had died after the November election but before the electors met in December).