Would Bernie be a drag on vulnerable Democrats?

The political scientist Robert Erikson has found that in post-World War II presidential elections, some voters may split their tickets against the party they believe will win the White House as a way to put a check on the likely winner, as opposed to waiting for the midterm two years later, when the president’s party customarily struggles. The public, along with analysts and betting markets, all saw Mrs. Clinton as a favorite in 2016. “Plausibly, many who thought Hillary Clinton would win voted Republican for Congress to block, thus accounting for the Democrats’ surprisingly feeble performance at the congressional level in 2016,” Mr. Erikson wrote in the lead-up to the 2018 election…

A consequence of Mr. Trump’s chronically low approval ratings is that even if Americans ultimately decide he’s the lesser of two evils this fall, there may be some voters who back him only tepidly or anticipate his victory and don’t want his party to have total control of the government. Mr. Sanders being a potentially weak opponent doesn’t necessarily make the president a beloved incumbent.

That may work to the benefit of House Democrats, even as they now panic — rightly or wrongly — over the possibility of sharing the ballot with Mr. Sanders.