I will not call it president. It is a serial murderer and rapist.

[bucolic_frolic]

31. To answer 14A query - Reconstruction Era precedents that are now lost or irrelevant

You must return to Reconstruction to see how the US Army of occupation handled insurrection before and after 14A passage.

U.S. Grant was General of the Army (1866), Secretary of war (1867), and then of course President. As General of the Army he prevented some insurrectionists from holding elected office, particularly in Louisiana. A US Senator-elect was prevented from taking his seat by vote of the US Senate. [This from the book Klan War By Fergus M. Bordewich]
https://www.penguinrandomhouse.com/books/647165/klan-war-by-fergus-m-bordewich/

Reconstruction remains a lightly touched subject. We are very late to learning the lessons of it.
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https://www.citizensforethics.org/reports-investigations/crew-reports/past-14th-amendment-disqualifications/

At least eight public officials have been formally adjudicated to be disqualified and barred from public office under Section 3 of the Fourteenth Amendment since its ratification in 1868.

Section 3, also known as the Disqualification Clause, has gained new relevance in the wake of the January 6th insurrection, when a violent mob that then-President Trump summoned and urged to “fight like hell” seized the United States Capitol to disrupt the peaceful transition of power. Adopted after the Civil War to protect American democracy from those who sought to destroy it, Section 3 disqualifies from office anyone who swore an oath to support the Constitution as a federal or state officer and then engaged in insurrection or rebellion against it, unless Congress removes the disqualification by a two-thirds vote.

CREW analyzed historical records to identify all public officials who a court, legislature, or other body determined to have been disqualified under Section 3. The list includes six officials aligned with the Confederacy who held office after the Civil War, as well as former New Mexico County Commissioner Couy Griffin, who a state court removed from office last year based on his participation in the January 6th insurrection following a lawsuit CREW brought on behalf of three New Mexico residents.

Section 3 adjudications against former Confederates were rare in the aftermath of the Civil War. That is because it was widely understood that former Confederates who took an oath to support the Constitution before the Civil War were disqualified under Section 3 and therefore many likely did not seek office in the first place. In fact, ex-Confederates flooded Congress with thousands of amnesty requests to “remove” their Section 3 disqualification, demonstrating that they understood themselves to be disqualified even without a formal adjudication. In addition, the window for disqualifying ex-Confederates was small: the Fourteenth Amendment was ratified on July 9, 1868, and Congress removed the Section 3 disqualification for most ex-Confederates less than four years later in the Amnesty Act of May 22, 1872 (that statute withheld amnesty from Confederate leaders such as Jefferson Davis). So while only eight officials have been formally ruled to be disqualified under Section 3, thousands more were understood to be disqualified in the period between the Fourteenth Amendment’s ratification in 1868 and Congress’s passage of the Amnesty Act in 1872 that applied to former Confederates.

[Much more at the above link]
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https://en.wikipedia.org/wiki/Unseated_members_of_the_United_States_Congress
Both houses of the United States Congress have refused to seat new members based on Article I, Section 5 of the United States Constitution which states that:

"Each House shall be the judge of the elections, returns and qualifications of its own members, and a majority of each shall constitute a quorum to do business; but a smaller number may adjourn from day to day, and may be authorized to compel the attendance of absent members, in such manner, and under such penalties as each House may provide."

This had been interpreted that members of the House of Representatives and of the Senate could refuse to recognize the election or appointment of a new representative or senator for any reason, often political heterodoxy or criminal record.