Is the crisis putting the Republican Senate in jeopardy?

The potentially awful news for Republican Senate candidates is another historical trend: the increasing link between votes cast for a Presidential contender and votes cast for senators, which makes it harder to create distance from an unpopular incumbent.

It wasn’t that long ago that ticket-splitting was commonplace. In 1992, 10 Senate candidates were elected from states that had given their electoral votes to the other party. But as party identification became more and more the key indicator of how votes were cast, this impulse all but disappeared. In 2016, every victorious Senate candidate came from a state whose presidential votes had gone to the same party. The days when Republican Al D’Amato could retain his New York Senate seat in the wake of a million-vote plurality for Bill Clinton in 1992 seem a distant memory.

Now turn to the Senate map, and it’s clear how these factors combine to produce a migraine for any strategist looking to hold the Senate for the Republicans. Not that long ago, Republicans were a good bet to hold the Senate even though they held 23 of the 35 contested seats. Only two—Cory Gardner of Colorado and Susan Collins of Maine—were in states that Hillary Clinton carried in 2016. Even with Arizona and North Carolina as potential Presidential battlegrounds, that left at most four vulnerable Republicans. And with Alabama Democrat Doug Jones a very likely loser, there was little breathing room for Democrats to pick up the three net seats they’d need to capture the Senate, assuming Biden wins in November.