How would William Jennings Bryan vote in the 2020 election?

[Alben Barkley]

I don't think the thought of voting for Trump would ever even enter his mind as an option. From WJB's perspective, Trump would have been among the most unsavory options ever nominated by the two parties

You'd think so, but then again I'd have thought the same of a lot of evangelical Christians who are today Trump's most rabid supporters. The mental gymnastics they use to justify their hypocrisy to themselves are really something. Combine that with Trump's economic populism (however phony it may be, and however far removed it is in many ways from Bryan's economic populism), and it's not impossible for me to see Bryan supporting Trump.

I'd like to agree with you, and I could believe that Bryan would be among the minority of principled evangelical Christians who refused to join Trump's cult. He could just as easily be out there railing against Trump as a false prophet if not the antichrist as he could be a member of the cult himself. But in any case I have a hard time seeing him supporting Biden (a papist!) or the modern Democratic Party due to social issues alone. If we follow his two most defining traits -- devout evangelical Christianity and economic populism -- and see how people who share those traits vote today, the odds simply point to him being more likely than not a Trump voter. That does, of course, not take into account Bryan's unique individual qualities and personality, which is why I say it's still quite possible he wouldn't support Trump. But it can't be ruled out either.

[Alben Barkley]

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.

The bolded is false. Some ostensible supporters unaffiliated with the Clinton and even Obama campaigns produced buttons with the Confederate flag, but they were never endorsed or produced by these campaigns.

This undermines a key part of your argument, frankly. I really don’t think Bill Clinton has changed all that much in 30 years.