In the short term, the president’s party is relatively insulated from midterm losses in the Senate, since only one-third of the seats are up for grabs. And the president’s party usually doesn’t have to defend much in its first midterm, as it has often already lost many of the contested seats six years earlier — when the party out of power fared well en route to last winning the White House. The same thing insulates some Democratic losses in 2022.

But if 2024 represents an opening for a Democratic bounce-back in the House, it may not offer as favorable an opportunity in the Senate. Democrats will have no opportunity to reclaim any Senate seats they might lose in 2022. And they will need to defend the seats they won six years earlier, in their 2018 midterm rout, including some in otherwise reliably Republican states such as West Virginia, Ohio and Montana. To hold or regain the Senate — and a trifecta — they might need all of those seats.

The Democratic grip on the Senate is dependent on holding Republican-leaning states because the Democrats are at a significant disadvantage in the chamber. The party tends to excel in a relatively small number of populous states, but every state receives two senators, regardless of population.