Depends on when, and what views they would have at a specific moment. If Obama ran today, he would win in a landslide. Bill Clinton would lose and do worse than Hillary.
Bill Clinton even aknowledged that he would not be able to win his home state of Arkansas today as it became so much conservative.
Are we talking about 1992 Bill Clinton or 2020 Bill Clinton, if it's 1992 Clinton Trump wouldn't stand a chance. 2020 Clinton then probably Trump.
I mean, to keep things consistent I’d assume a 1992 Bill Clinton (or alternatively a 2000 outgoing Bill Clinton), otherwise Trump would win in landslides against 2020 LBJ, 2020 Truman, and 2020 JFK, all of whom are dead.
1992 Bill would crush Trump, though he’d obviously lose Arkansas. I’m thinking a 2008-esque map but with Arizona.
2000 Bill honestly might put in a similar performance to 1992 Bill since he’d be riding his end-of-presidency approval ratings and he happens to be facing the only modern-day presidential candidate with more sexual-assault claims to his name, which would more than neutralise the effect of that incident that happened in his second term. Trump would probably try to bring his accusers to the debates again, not that that would do much good. Probably something like 340-218?