Midterm Election

Midterm elections occur every four years exactly halfway between presidential elections, filling all 435 House seats, roughly a third of the Senate’s 100 seats (since senators serve staggered six-year terms), and numerous state and local offices, all without a presidential race on the same ballot. The President’s party has lost House seats in nearly every midterm election of the past century, a pattern so consistent political scientists treat it as close to a structural rule rather than a coincidence, generally attributed to lower midterm turnout skewing toward the opposition party’s more motivated voters, and a natural correction after the winning party’s coalition inevitably disappoints at least some of its own supporters once actually governing.

The most dramatic recent midterm example came in 2010, when Democrats lost 63 House seats, the largest House seat swing in any midterm since 1938, following the passage of the Affordable Care Act and amid a slow economic recovery from the 2008 financial crisis — a wave large enough to flip House control entirely to Republicans for the remainder of President Obama’s first term.

Common misconception: people often assume a President’s party performance in a midterm mainly signals a straightforward referendum on that President’s approval rating alone. While presidential approval does correlate with midterm outcomes, the pattern of the President’s party nearly always losing seats holds up even for presidents with relatively strong approval ratings at the time, suggesting structural factors (lower and more skewed turnout, an energized opposition, the drop-off from a peak presidential-year coalition) play a significant role independent of any single president’s specific popularity.