Here's a hot take. The democratic incumbents in red states who won election/reelection in 2012 in an environment that was only slightly less polarized then 2016 aren't heavy underdogs in a year that will almost certainly be at least a decent D wave. Even bigger hot take. Republicans aren't going to knock out popular swing state incumbents in a midterm under a Republican president whos 20 points underwater nationwide.
Two of those incumbents won solely because their opponents were wackos who imploded after making incredibly dumb comments. And that's probably not going to happen twice.
Also, we really don't know if Trump's approvals will stay like this on election day.