Democrats are hoping for a wave election next year that regains them control of the U.S. House of Representatives (the Senate, with its massively pro-GOP 2018 landscape, is probably out of reach). Though the number of House seats they need to flip (24) is relatively high, it’s a benchmark that that each party has achieved in the recent past (Democrats in 2006, Republicans in 1994 and 2010). And they have some of the raw materials for big gains at hand: an unpopular Republican president; 23 GOP-held House districts that were carried by Hillary Clinton last year; and a big lead in the congressional generic ballot (the RealClearPolitics average shows Democrats up by 7.8 percent at present — close to the 8 percent margin they won in 2006 when they picked up 31 seats and won back the House for the first time since 1994).
Republicans do, however, have some factors that could help them hang onto control next year. They have some opportunities of their own, beginning with the 12 Democratic-held House districts Trump carried in 2016. Past gerrymandering (built on the 2010 GOP landslide and augmented by aggressively partisan redistricting at the state level) has narrowed the landscape of competitive districts and made the Democratic popular-vote margin needed to flip seats significantly higher (viz. the 2012 House races, where Democrats won a plurality of the national popular vote but fell well short of a majority of seats).
And there’s one more asset they may or may not enjoy that gets a lot less attention than it should: incumbency. As Nate Cohn recently explained, incumbents generally do better, all other things being equal:
Over the last decade or so, incumbents have run about seven percentage points ahead of non-incumbents from the same party in similar districts. That’s more than enough to let incumbents in competitive districts survive, even in so-called wave elections like the ones that swept Democrats into power in the House in 2006 and back out in 2010.
It’s early in the cycle, and the math on incumbency is sometimes complicated by noncompetitive districts where it really does not matter if there’s a retirement. But four House Republicans in potentially competitive districts have retired so far. Yesterday another House Republican, scandal-plagued Tim Murphy of Pennsylvania, resigned his seat, creating a special election in a Republican-leaning district that could create an opportunity for Democrats, but not necessarily. But then Carol Shea-Porter, a Democratic incumbent in a much more competitive district (it has changed hands five times in the last six elections) in New Hampshire announced her retirement today.
How many more GOP retirements do Democrats need to give them a good chance to regain the House if the other factors (i.e., Trump’s unpopularity and a generic ballot advantage) stay pretty much the same? Cook Political Report’s David Wasserman suggests that five more among 48 Republicans in competitive districts would make “Democrats’ route to the majority…become much more realistic.” Nate Cohn notes the history:
Since 2004 (and excluding 2012, because of redistricting), around 15 percent of the president’s party’s incumbent representatives in potentially competitive districts have retired in an election cycle on average. This time, that would translate to seven retirements — or three more than the four so far. Moving 15 percent of the way from 213 to 240 would be enough to make the fight for control of the House a true tossup, as prediction markets and most analysts seem to expect.
So the retirement watch should get just as much attention as the other, more frequently discussed variables for 2018. And that’s what also makes threats of GOP primary challenges by Steve Bannon or other “insurgents” dangerous, if they spill over from the current target list of senators to competitive Republican-held House districts. Anything that gives GOP incumbents happy feet is good and important news for Democrats.