After August’s long congressional recess, retirement is suddenly looking pretty good to many Republican members of Congress. On Monday, Rep. Dave Trott of Michigan’s 11th Congressional District became the latest in a string of Republicans to step away from competitive U.S. House seats. The rapid-fire retirements have quickly given rise to the narrative that the unpopularity of President Trump — which threatens to hang like a lead weight around Republican candidates’ necks in 2018 — is scaring Republicans straight off the ballot.

At first glance, the list of retiring congresspeople fits that narrative pretty well. Of the 24 members who have thus far decided not to run for reelection in 2018, 16 are Republicans and 8 are Democrats. But it’s not immediately clear that electoral endangerment is the reason for that lopsidedness.

Most House members not seeking re-election are Republican PARTY INCUMBENT DISTRICT SEEKING HIGHER OFFICE PARTISAN LEAN OF DISTRICT* R Diane Black TN-06 ✓ -49.2 R Evan Jenkins WV-03 ✓ -47.5 R Raúl Labrador ID-01 ✓ -39.4 R Luke Messer IN-06 ✓ -38.6 R Todd Rokita IN-04 ✓ -34.1 R Kristi Noem SD-AL ✓ -29.4 R Lou Barletta PA-11 ✓ -22.7 R Jim Renacci OH-16 ✓ -17.1 D Tim Walz MN-01 ✓ -13.4 R Steve Pearce NM-02 ✓ -11.9 D Jacky Rosen NV-03 ✓ -3.1 D John Delaney MD-06 ✓ +11.8 D Michelle Lujan Grisham NM-01 ✓ +13.8 D Jared Polis CO-02 ✓ +18.0 D Colleen Hanabusa HI-01 ✓ +32.0 D Beto O’Rourke TX-16 ✓ +35.4 R John J. Duncan Jr. TN-02 -38.2 R Sam Johnson TX-03 -20.7 R Lynn Jenkins KS-02 -19.6 R Charlie Dent PA-15 -9.0 R Dave Trott MI-11 -7.2 R Dave Reichert WA-08 +0.1 R Ileana Ros-Lehtinen FL-27 +13.9 D Niki Tsongas MA-03 +18.5 * The partisan lean of the district is relative to the nation as a whole. It is calculated by combining the district’s 2016 presidential lean with its 2012 presidential lean; 2016 results are weighted 75 percent, and 2012 results are weighted 25 percent. Source: Roll Call, Daily Kos Elections

Only two of the departing Republicans occupy Democratic-leaning seats, and the same number of departing Democrats occupy Republican-leaning seats. The fact that there are simply more Republicans than Democrats in Congress overall looked like a better explanation for the Republican-heavy roster of retirees so far — at least until this month, when three successive swing-seat Republicans (Dave Reichert, Charlie Dent and Trott) have called it quits.

However, the data may be skewed by the fact that many of these members aren’t retiring at all — they’re actually seeking a promotion to higher office. When you narrow down the list to just those representatives who are truly retiring, the pattern starts to change. Just one Democrat, Niki Tsongas, is going home for good, and her Massachusetts 3rd District was never expected to be competitive. Seven Republicans, meanwhile, are leaving politics, including all four (Reichert, Dent, Trott and Ileana Ros-Lehtinen) who sit in vulnerable seats.

The pure retirements, so far PARTY INCUMBENT DISTRICT DEMOCRATIC LEAN OF DISTRICT* R John J. Duncan Jr. TN-02 -38.2 R Sam Johnson TX-03 -20.7 R Lynn Jenkins KS-02 -19.6 R Charlie Dent PA-15 -9.0 R Dave Trott MI-11 -7.2 R Dave Reichert WA-08 +0.1 R Ileana Ros-Lehtinen FL-27 +13.9 D Niki Tsongas MA-03 +18.5 * The partisan lean of the district is relative to the nation as a whole. It is calculated by combining the district’s 2016 presidential lean with its 2012 presidential lean; 2016 results are weighted 75 percent, and 2012 results are weighted 25 percent. Source: Roll Call, Daily Kos Elections

The retirement press releases flowing out of the Capitol jibe with what political scientists have long suspected. A 1999 study (aptly titled “You Can’t Fire Me, I Quit”) found some evidence that politicians are more likely to retire when they believe they’re in for a tough race. But here’s the thing — what politicians believe will happen in the election and what actually happens aren’t always the same thing. Historically, there has been a correlation between the party with the most retiring members and the party that loses the subsequent election, but it’s not all that strong.

The party with the most retiring members doesn’t always lose the most seats RETIRING SEAT SWING IN ELECTION ELECTION CYCLE DEMOCRATS REPUBLICANS SENATE HOUSE 2018 1 7 ? ? 2016 10 20 D+2 D+6 2014 15 16 R+9 R+13 2012 21 14 D+2 D+8 2010 14 13 R+6 R+63 2008 3 27 D+8 D+21 2006 6 9 D+6 D+30 2004 10 13 R+4 R+3 2002 7 16 R+2 R+8 2000 7 18 D+4 D+3 1998 15 11 0 D+5 1996 28 18 R+2 D+9 1994 25 9 R+8 R+52 1992 35 23 0 R+10 1990 5 9 D+1 D+8 1988 10 10 0 D+2 1986 10 13 D+8 D+5 1984 4 9 D+2 R+14 1982 13 12 R+1 D+26 1980 20 11 R+12 R+34 1978 28 13 R+3 R+15 1976 24 11 0 D+1 1974 16 21 D+5 D+48 Does not include officials leaving their position to run for another office. Independents are counted as members of the party with which they caucused; members who resigned or died before the election are not counted. Sources: Roll Call, Ballotpedia, Center for Responsive Politics, The American Presidency Project

Sure, more Republicans than Democrats retired in 2008, and the GOP got walloped in November. But more Republicans than Democrats also retired in 2014, which ended up being a Republican wave election. Yes, a sizable number of Democrats retired in 1994, accompanying a Republican wave. But even more Democrats retired the following election cycle, when the party gained back some of its losses.

A rash of retirements doesn’t necessarily signal a wave election, and (predicted) waves don’t necessarily spur more retirements. Instead, the pattern of retirements appears to be generational as well as about representatives responding to the political environment. Republican retirees have outnumbered Democratic ones in most election cycles since the mid-1990s; for the 20 years before that, Democrats usually retired at higher rates than Republicans. Members of big freshman classes like 1994’s and 1974’s have to hang up their spurs sometime.

That said, the most fundamental takeaway is still this: Retirements from a competitive state or district hurt the party the member belongs to. The reason is simple: incumbency advantage. It’s easier, for example, for a Democrat to win in a slightly red district in an open election than to take on a sitting House member. The more Republicans in competitive districts who retire heading into 2018, the more seats Democrats can realistically go after.

And there may yet be plenty more. At 24 announced open seats so far this year, we are still a long way from the 40 or so total that is normal for recent cycles. Keep an eye on how many more retirements are in the offing; the more Republicans who head for the exits, the worse 2018 could be for the party.

Andrea Jones-Rooy contributed research.