"Section 3 Disqualification from Holding Office
"No person shall be a Senator or Representative in Congress, or elector of President and Vice-President, or 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, or as a member of any State legislature, or as an executive or judicial officer of any State, to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof. But Congress may by a vote of two-thirds of each House, remove such disability."
The Supreme Court of Colorado and the Secretary of State of Maine have both declared Donald Trump ineligible for the presidential ballot under this provision of the constitution. The case is already on its way to the Supreme Court, which will have to pass on it. Should the court deny the states the right to take this step, they would in my opinion betray the "originalism" which several of the justices claim to be the foundation of their jurisprudence. That is not only because of the plain meaning of these words, but because of the history of their application during the four years in which this provision remained in effect after the ratification of the 14th Amendment, from 1868 until 1872, when Congress, following the text of the provision, removed the disability from nearly all former confederates except the top leadership. That history is summarized by this excellent web article, which I encourage you all to read in full, and which I will summarize.
Critically, it is very clear that one did not have to be criminally convicted of insurrection in the wake of the Civil War to be disqualified from office. Almost no confederates were ever formally charged with rebellion, but thousands of them recognized the applicability of the clause to themselves, in effect, by petitioning Congress to remove their disability. The article lists six men who assumed state or federal offices and were removed from them after judicial proceedings in state courts or federal court (as has happened to Trump in Colorado); by state executive officials (as has happened to him in Maine); or because Congress refused to seat them, citing section 3. None them had been convicted of any crime relating to insurrection. The reason conviction was not necessary, the article argues, was that disqualification from office is not a criminal penalty. In addition, in one case, the Governor of Georgia refused to certify victorious candidate for the House of Representatives on the grounds that he had engaged in the rebellion, suggesting that states could act against ineligible candidates for federal office. (The House of Representatives also refused to seat that candidate, however.) The article also notes that section 3 was interpreted to apply to anyone who had advocated rebellion, whether they had specifically rebelled themselves or not. Nor does it seem out of place for me to point out that the Democratic Party in the post-Civil War era never nominated anyone from the old Confederacy for either president or vice president, even after Congress acted to remove the restriction on nearly all ex-confederates in 1872. Such people were likely to have fought for the Confederacy and remained disqualified in fact if not by law.
Two men have been disqualified from holding office under the clause in subsequent eras. Victor Berger, the Socialist mayor of Milwaukee, opposed US entry into the First World War, leading to his indictment--along with many other fellow socialists, such as Eugene V. Debs--under the Espionage Act. He was elected to Congress while under indictment in November 1918, convicted in February 1919, and denied his seat by the House of Representatives when it met in December 1919 under section 3 of the Fourteenth Amendment. His conviction was eventually overturned and he returned to Congress in 1923, after having been defeated in the Republican sweep of 1920. Interestingly enough, however, there seems to have been no attempt to keep Debs of the ballot in 1920, when he ran for president on the Socialist ticket while serving his sentence and won nearly one million votes. More recently, a New Mexico state court disqualified a man from holding office as a county commissioner because he had been convicted of trespassing during the January 6 insurrection at the Capitol--confirming that the clause is very much alive.
The history of the application of this clause from 1868 into 1872, and more recently in New Mexico, suggests to me that the authorities in Colorado and Maine are historically well within their rights to conclude that Donald Trump participated in an insurrection and thus is now ineligible to hold any office under the United States, and therefore ineligible for the ballot for nomination or election in their state. (The argument that section 3 does not apply to the presidency is, in my opinion, utterly without merit.) Other states might do the same--but they would almost certainly be solidly blue ones, whose loss would not cost Trump any electoral votes. (The Maine ruling would have cost him one electoral vote, based on his victory in one of Maine's two congressional districts, in 2020, but Biden carried the popular vote in both Maine and Colorado quite comfortably.) Meanwhile, the denial of certain states to Trump would probably energize his supporters in the critical purple states still further. The Supreme Court will almost certainly not be asked if the federal courts could deny Trump the right to receive any electoral votes at all, and it is hard to imagine that this court would do so anyway. In theory either house of Congress could vote not to certify a Trump victory on the grounds that he was ineligible to serve under section 3, just as the House several times refused to seat members on those very grounds, but that, it seems to me, would almost surely result in a new civil war of some kind.
The government of the United States could summarily bar many thousands of former office-holders from any role in government in 1868 because it had put down their rebellion by force during four years of almost total war. We are in danger today because our government does not now enjoy comparable prestige and the country is still deeply divided over whether Donald Trump tried to overthrow the government or not. I am not even sure that Trump's conviction for attempting to overturn the election, either in Georgia or in federal court, would change the situation very much, because even then, roughly half the country would reject attempts to disqualify him. The failure over the last twenty years to renew confidence in our Constitution and our institutions threatens terrible consequences.