I think a lot of it would boil down to whether suburban moderates dislike Trump more than they dislike Bernie. There's arguments to be made either way (or they just stay home).
It's not like Trump is broadly popular. He won the election by a combined 100,000 votes in three states, his approval ratings are low and have really never climbed since he took office, despite the strong economy and all he's done to consolidate Republican support. A lot a lot of Americans really do not like him.
I think Trump can count on the Red States. Any Dem can count on the Blue states. In the 10 or so swing states Trump will do well with white voters, rural voters, religious voters, and the Dem will do well with urban voters, nonwhite voters and probably well-educated women. Seems like both parties' bases will be highly motivated. So much feels baked-in at this point. So basically it comes down to normal moderate voters, particularly women, in places like suburban Philly and Detroit and Denver and Phoenix.
For what it's worth, I think Bernie is about the worst possible major Dem to appeal to those folks. But I don't think they love Trump either. They certainly didn't in 2018 when the Dems routed the suburbs by running normal moderates. Will they go for Bernie? Trump? Stay home? I'm not sure we'll know either way until the votes start coming in.
