It's a current liberal fantasy - by which I mean: something that *should* happen, but almost certainly *isn't* going to - that Trump will be disqualified from running for President in '24, due to his prior involvement in fomenting an insurrection against the United States of America.
This is what the 14th Amendment, Sec. 3 to the Constitution, written in the aftermath of the Civil War, clearly provides for. But of course, politics gets in the way whenever a harsh rule like this is actually meant to be applied.
"You can't take a question like that away from the voters! You're undermining democracy!! Let the voters decide!!!"
Of course, the same people who make that argument on behalf of Trump are the same people who rejected what the voters clearly said in '20. But I digress.
If Trump is ultimately denied the GOP's nomination in '24, then from a purely self-interested perspective, Democrats should instead hope that Trump *isn't* somehow disqualified from running for President in '24.
Because Trump would totally do everything in his power to burn the GOP to the ground if he is no longer allowed to rule the roost, up to and including running a doomed third-party campaign. Heck, Trump might not even do it out of spite, though I'm sure he'll have plenty of that. He might do it simply because he's a toxic narcissist with a compulsion to self-promote and seek the spotlight by any means necessary. He might also think keeping the facade of being a plausible presidential candidate up for as long as he can will somehow advantage him in the legal cases pending against him, though it won't.
Anyway. A third-party Trump campaign in '24 that claimed even 5% of the vote - and Trump, a former President with a cult following, would probably win a lot more than that - would be fatal to the GOP's ability to defeat a Democrat.
The historical precedent for something like this is the 1912 election, when Teddy Roosevelt - who was many things, but for purposes of this example, a bull-headed egomaniac - ran third-party for an unprecedented 3rd Presidential term (before this was made illegal) when denied the Republicans' presidential nomination, losing out to the incumbent President and Roosevelt's own handpicked successor, William Taft.
During a period of American history when Republicans traditionally dominated national elections, Taft and Roosevelt fatally split the Republican vote, resulting in the unlikely election of Woodrow Wilson, a Democrat.
Caption this Meme 