Now that 2018 shows signs of being the next Democratic wave year, it’s possible that once again Tester’s boat—and McCaskill’s, and Manchin’s, and all the rest—will be lifted. After all, in four of the five instances when the House changed control since World War II, the Senate has flipped along with it.

But there are crucial differences this year. Perhaps the biggest is that Trump has signaled his intent to leverage his popularity against Democratic Senate incumbents in the states where his approval ratings are strongest. His presidential travel schedule has closely overlapped the roster of states he carried in 2016. Trump could decide to try to zero in on Tester or another red-state Democrat with a disparaging nickname and a barrage of October tweets.

Then there’s the end of Blankenship. Democrats have feasted on Republican freak-show candidates in recent Senate elections. Donnelly and McCaskill both skated to victory in 2012 after their challengers made controversial remarks about rape, pregnancy and abortion.