If he dies tomorrow, Vance comes in- and can only run for ONE more term.

Vance doesn't have the intense personal loyalty Trump has from the Revelationists(my term for those who call themselves "evangelical Christians", because the only thing they care about in the Bible is the end of the world part) and the alt-reich, so they may not feel the same obsession with fighting to the bitter end on his behalf. Also, Vance can't connect with an audience in the way Trump can.

At least, that's the hopeful scenario.