Mr. Trump's increasingly disjointed public appearances have made it evident that he doesn't have the mental capacity to make it through a full term in office - maybe not even the first year. That of course raises the question of the 25th Amendment, which in turn leads to a political dilemma for Solons of both parties. Let's suppose that he and Senator Vance are elected, and that some time later Vice President Vance (as he would then be) and a majority of the Cabinet inform Congress that the President can't perform his duties.
That's fine, if President Trump (as he would then be) agrees . . . but if he doesn't agree, and notifies Congress that he believes himself to be fit to serve, then Congress must vote, and he would return to power unless two-thirds of the House and two-thirds of the Senate vote that he is in fact incapacitated and unable to serve. Neither party will hold two-thirds of the seats in either chamber, meaning that Mr. Trump would return to the presidency unless Democrats join with republicans to oust him . . . in favor of J.D. Vance.
Will the republicans, up to now mostly servile, vote to eject Donald Trump from the presidency and risk the anger of their base? And will the Democrats vote to eject him, knowing that J.D. Vance will then lead the nation? The senators and representatives of both parties will have no correct answer.
The situation gets more complicated if Mr. Trump should resign or die in office. Vice President Vance will become the president, and the Speaker of the House will be next in line for the presidency until President Vance nominates a new vice president and a majority of both houses approve his choice. Imagine that the Democrats flip the House and choose (say) Hakeem Jeffries as the speaker. Would the Democrats, still remembering the non-hearing of Merrick Garland, be willing to vote down any nominee and keep the Veep position vacant? I think that turnabout would be fair play, and would enjoy watching the Senate republicans rage that the House is refusing to hold a hearing on a presidential nominee.