It marks just the third time since 1978 that either party has seen at least 30 retirements in a single cycle, according to figures tallied by the non-partisan Brookings Institution. The last instance was just four years ago, in the 2018 midterms, when 34 House Republicans made for the exits. It was a grim sign of things to come: The GOP went on to lose 41 seats — and the House majority — in a Democratic wave widely viewed as a referendum on then-President Trump.

This year, it’s President Biden’s Democrats who face the difficult terrain. Between Biden’s sagging approval ratings, a stalled policy agenda in Congress, nationwide redistricting, and the historical trend that the incumbent president’s party tends to lose seats in midterm elections, the odds of winning the House are increasingly in the Republicans’ favor.

Kyle Kondik, managing editor of Sabato’s Crystal Ball, a political handicapper at the University of Virginia, cited “a collision of important circumstances” creating fierce headwinds for Democrats, not least the redistricting process that, like a game of musical chairs, has left some lawmakers without their old districts — and pushed them into retirement.