What we see from this is that the decline in President Bidens’ job approval from around 52% to 46% is consistent with a loss of an additional 5% of the Democrats’ caucus, or an additional 11 seats. If we put them altogether into a single regression analysis, we explain about two-thirds of the overall variation. This isn’t so bad, given the amount of randomness we have to explain here. The model suggests overall that the decline in Biden’s job approval will probably cost Democrats about eight seats.

Some of this is likely blowback to the botched withdrawal from Afghanistan, which may recede over the coming months. It may also be the case that there is some reluctance on the part of Democrats to respond to surveys right now, which artificially deflates his job approval.

Regardless, the decline in Biden’s job approval is consequential. Right now, he is probably sitting just below the “Mendoza line” that would represent a “normal” midterm, with perhaps no Senate losses and low double-digit House losses. If the president rebounds, Democrats will have a successful 2022, even if they narrowly lose the House. If he declines much further, however, it could turn into an ugly rout.