The Midterms, Incumbency, and Washington, D.C.

It's conventional wisdom that anti-Washington sentiment threatens to scramble the midterm elections. But which incumbents should be most worried? A report in the spring issue of The American Journal of Political Science tracks the effect of Congress's overall approval rating on the performance of incumbent House candidates between 1976 and 2006. It finds that when people's opinion of Congress is near an all-time low, as it is today, majority-party incumbents slip an average of 12 points in polls, compared with years in which the public views Congress more favorably. The data give credence to predictions that this fall could be among the worst Democratic showings in decades.

Conversely, minority-party incumbents (in this case, Republicans) benefit when the national mood turns sour. During the past three decades, says Baruch College political scientist David Jones, the study's author, Congress's approval rating has averaged 37 percent. For each 10-point fall below that, the minority party has gained 17 seats—a ratio that could translate into more than 30 Democratic losses this November in the House. That's more than all but the most dour analysts have predicted. Democrats may have one hope: while Jones's data demonstrate a historical link between incumbency and vote share, an improved economy, he says, could matter most.