How would William Jennings Bryan vote in the 2020 election?

[RINO Tom]

All of these questions rely on one big question ... would this person retain absolutely static cultural and political views for his/her entire life, across multiple decades?  I guess some people do, but imagine an alternate world where Bill Clinton died in the late 1980s ... I imagine a lot of people would argue he might not have supported Obama or Biden, but he obviously did in real life.  His views changed with his party, because he probably had a stronger attachment to his overarching ideology than to specific stances of his ... he ran with a Confederate flag on his campaign posters in 1992, and he would not have in 2020 if he were running.  That doesn't mean HE changed all that much.

As for WJB, I would argue the issue most true to "who he was" as a politician is the opposition to what he saw as business excess and income inequality.  I'm sure he'd crow about Democrats becoming too culturally liberal, but would that be enough to make him line up with Mitch McConnell, Kevin McCarthy and even Donald Trump?  I'm doubtful, and I would say he'd vote for Biden after supporting someone else in the primaries.

[RINO Tom]

It depends if we're talking about him just snapping back to life, or somehow still being alive all this time.

If he's just 160 years old and has lived through the last 100 years, I think he would have stayed a Democrat the whole time and adjusted his social views accordingly. But if 1925 Bryan were reanimated in November 2020, yeah, he's going to have no concept of anything going on. I think he would have a strong dislike for Trump still though.

This is a great answer, and your first question is an absolute must for these hypotheticals, IMO.  Look no further than Bill Clinton, who was campaigning for President as a Democrat with a Confederate flag prominently displayed in 1992 and pretty much just tows the party line on social/cultural issues in 2023 ... "being a Democrat," it turns out, was a stronger aspect of his personality than anything to do with the Confederate flag, that flag was just simply more associated with a Democrat from Arkansas without controversy in 1992 than it is now.

On that same note, being a fundamentalist Christian from a rural area wasn't some no-go for WJB as a Democrat when he was alive, and it's not like part of his campaign against his Republican opponents had to do with his "socially conservative" views; he was very clearly focused on income inequality and proper (in his mind) regulation of corporations.  As you said, I think there is a bit more of a discussion to be had if a man of his era was just plopped down into 2020 and heard about things like transgender rights and whatnot for the first time, but I have little doubt that if he simply lived through each decade and never died, his economic views would remain the most important part of his philosophy.  And I think that would mean he's still a Democrat.