If you look at history, Trump isn’t the only politician who the crisis could take down.

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.

Now—at least measured by polls—a passel of states now seem within Biden’s reach, many of them with incumbent Republican senators up for re-election. He’s even in Georgia, where both incumbent Republican senators will be on the ballot; he’s even in Iowa, where Joni Ernst is up for re-election. And if Biden is going to make a real fight in Georgia and Iowa, that means a get-out-the-vote effort that will bring a lot of Democrats to the polls there.

Nor is it necessary for Biden to actually win a state to provide aid to a Senate candidate: In Montana, Democratic Governor Steve Bullock won re-election in 2016 while Trump was winning the state by 20 points. The most recent Presidential poll shows Trump leading in Montana by only five points; a margin that would give Bullock, now the Democrats’ Senate candidate, a real shot at unseating Steve Daines and flipping that seat to the Dems. A close race in North Carolina—which Trump carried by 3 1/2 points four years ago, and where he trails by four in the most recent survey—is a clear and present danger to Senator Tom Tillis. (Most recent surveys show Trump falling further behind Biden in the wake of his disastrous leadership in the George Floyd case—although if job numbers continue this week’s apparent turnaround, Trump’s fortunes could improve.)