Today is the last day a governor might replace a House Representative who resigns. Coincidentally, one Republican Congressman has announced that he will resign on April 19th, tomorrow. As of that point, the makeup of the House will be 217 Republicans and 213 Democrats.
Marjorie Taylor Greene has already threatened to introduce a motion to vacate the chair, and Thomas Massie has indicated that he will support a move to bump Mike Johnson out of the Speakership. Let's assume the Republicans have a death-wish and will carry that plan through.
If Johnson is removed as Speaker, the Democrats will nominate Hakeem Jeffries as Speaker. Only three never-Trump Republicans are needed to hand the gavel to Jeffries on a 216-214 split; all the Democrats will support Jeffries, and all three branches will then be controlled by a single party.
The first order of business for the new Speaker will be to pass a very short bill declaring that Donald Trump committed insurrection on January 6th, 2021. The Democrat-controlled Senate will pass that bill the same day, and it will be rushed over to 1600 Pennsylvania where a Presidential aide will shake Biden awake and say "Joe, wake up; sign this."
Suddenly, as with the stroke of a pen, it will become a non-starter for the Republicans to nominate Trump as their Presidential candidate since he will be unable to assume that office even if elected. By 2028, Trump will be too old to be a viable candidate. His political career will be over. Nikki Haley will be the Republican nominee, and it won't matter who wins because the end product is the same.
Yes, of course, such a move by the Democrats will be overturned by SCOTUS since it denied Trump the due process the Constitution demands, but by then it will be 'all over but the shouting'.
Are the Republicans stupid enough to score an own-goal? Alas, it appears the answer is 'yes'.