Trump getting a second term seems to drastically increase the likelihood of a civil war, whereas Biden remaining in office drastically favors WWIII. Screwed either way, and I'm not sure which one is the lesser evil...
Trump would be civil war AND WWIII. The dude already said he's for the genocide of Gaza and everyone knows he loves Russia and China. He would also end Democracy within the US.
For a Trump presidency, do you mean a civil war happening during WWIII? Because that man wouldn't do jack shit about stopping that from happening. He'd just join his buddy Putin's side of that conflict, supposing the civil war resolved in his favor. And supposing WWIII's nuclear Armageddon ending isn't reached before that point.
Trump doesn't need that threat held over his head; he's a Putin fanboi and true believer.
Trump has zero shame. If there were such a tape and it were actually effective at blackmailing him, I'm willing to bet it it's because it's a "CP" tape, not just a "pee" tape.