Broadly, it's very simple.
Make a list of everyone, ranked in order of personal wealth from most to least.
That's also a ranking, in order, of winners to losers under Trump.
Though exceptions will of course be made for rich people who piss him off and poor people who suck up to him and can provide something he wants.
I sincerely have no idea.
The narrative that a leftist couldn't win is repeated so predictably and so often and by so many people that the whole idea has become sort of detached from reality, and there's no telling what would happen if it was actually a possibility.
And particularly since the one thing I'd pretty much guarantee is that the concerted efforts on the part of the ruling class to prevent a leftist from running would be as nothing compared to what they'd do and say in order to prevent one from winning.