If and when President Trump mounts another bid for the presidency, he will face a legal challenge aiming to disqualify him from office before a single vote is cast. 

That is the vow of a nonprofit, Citizens for Responsibility and Ethics in Washington, threatening to use the Disqualification Clause of the Constitution’s 14th Amendment to block Mr. Trump from the ballot. A letter to Mr. Trump at his compound in Florida was sent by the committee’s president, Noah Bookbinder, a former aide at the Senate Judiciary Committee.

The Bookbinder letter warns the former president that the organization will “pursue your disqualification under Section 3 of the 14th Amendment.” The note goes on to tell Mr. Trump that the nonprofit believes he is “barred from holding office under” because he “engaged in insurrection against the Constitution you swore to defend.”

Mr. Trump has been tried once in connection with the events of January 6, 2001, when the House brought him up before the Senate on a charge of “incitement to insurrection.” At the trial, though, the Senate acquitted the former president, declaring Mr. Trump “not guilty.”

Yet Mr. Bookbinder argues that by “summoning a violent mob to disrupt the transition of presidential power mandated by the Constitution after having sworn to defend the same,” Mr. Trump rendered himself “ineligible to hold public office again.” 

That provision of the post-Civil War amendment allows for the disqualification of anyone who has already held a public office from holding “any office” if they “engage” in an “insurrection or rebellion” against America. Despite the finding by the Senate of “not guilty,” the case that Mr. Trump “engaged in insurrection as contemplated by the 14th Amendment,” is, according to Mr. Bookbinder, “overwhelming.”

This is not the first time the specter of disqualification has been raised against Mr. Trump. In July, a liberal legal advocacy group, Free Speech for People, asked every secretary of state in America to sign a declaration affirming its conviction that the former president is “ineligible to appear on the presidential primary ballot.”

In September, a New Mexico judge ordered the Otero county commissioner, Couy Griffin, be removed from office. Judge Francis Mathew ruled that the events of January 6 constituted an insurrection, the first judge to do so. 

Judge Mathew further held that Griffin — who had been convicted of criminal trespassing for his actions that day — was barred from present and future office under the Disqualification Clause for spending “months normalizing violence” and for storming the Capitol. 

After lying dormant for more than a century — the clause was last deployed against a socialist congressman, Victor Berger, in 1909 — it has enjoyed something of a renaissance following the events of January 6, 2021.

Earlier this year, Free Speech for People mounted challenges to Representatives Madison Cawthorn and Marjorie Taylor Greene under the Disqualification Clause’s banner. Mr. Cawthorn notched a district court victory and an appellate defeat, only for the challenge to be mooted when he lost in the Republican primary.

Mrs. Greene will be on the November 8 ballot after a state administrative law judge refrained from barring her from standing for re-election, a decision that was left undisturbed by the Georgia secretary of state, Brad Raffensperger, and state courts. Other disqualification efforts in Arizona and Wisconsin likewise petered out.  

Now, the highest-profile disqualification battle of all has been joined. Mr. Bookbinder ends his letter with the promise that “we and others loyal to the Constitution” view disqualifying Mr. Trump as crucial to restoring the “fundamental expectation that sustains our democracy — that the American people elect their leaders and that government leaders accept those results.”