>>[2136 book idea]....a world in which 80 percent of the population has been wiped out by climate change, but also a world where characters time-travel to create an alternate past in which Clinton won the election.

If I was time-traveling back from the far future, I feel like the more relevant inflection point would have been to drop in on the year 2000 and create a past where Gore wins the election.

Not only would that be a more impactful long-term change that would likely have prevented the systemic failures that elevated Trump in the first place, but it would probably be easier to enact. You just need to park a handful of people outside a handful of voting precincts to say "Hey, just so you know this ballot is really badly designed. . ."

No first Black president, though. So we'd have to deal with that.