Rep. Darrell Issa (R-Calif.) speaks to reporters after attending a closed meeting with Deputy Attorney General Rod J. Rosenstein in May 2017. (Astrid Riecken for The Washington Post)

An unusually large number of Republican members of the House have announced that they plan not to seek reelection this November. How unusually large? According to a tally by Daily Kos, there have been 30 announced retirements, including 11 announced retirements among Republicans seeking another office. Since 2006, the previous high was 29 announced Republican retirements — before Election Day. We still have months to go during which more retirements might be announced; we saw two Republican retirements this week alone, among them, Rep. Darrell Issa (R-Calif.).

As Nate Cohn at the New York Times noted on Tuesday, though, that doesn’t mean the Democrats are on the brink of picking up 30 seats from the Republicans. First, they have 15 retirements of their own. Second, most of the seats being given up by Republican representatives are in districts that are safe for the GOP. By Cohn’s estimates, 13 seats held by retiring Republicans are competitive.

On Wednesday, Cook Political Report’s Dave Wasserman unveiled data suggesting that the Democrats should do pretty well in those 13 seats.

This gets tricky fairly quickly, so we’ll reiterate Wasserman’s point with an example. If Rep. Smith is a Democrat who was retiring before the 2014 elections and his district voted for Mitt Romney in 2012, the Republicans ended up winning Smith’s seat. No exceptions.

I decided to see what happened in each retiring member’s district since 2006, leveraging that data from Daily Kos (including data on how congressional districts voted in presidential races). Operating under the assumption that the more interesting races were those in which members were retiring not to run for office — suggesting that they were perhaps worried about the electoral climate — we figured out how each of those 131 districts voted in the preceding presidential race and how it voted in the ensuing House race.

The results jibed more with Cohn than Wasserman. The vast majority of retirees were replaced by members of the same party (97 of the 131). In the 25 races where the presidential preference in the district was for the party to which the retiree didn’t belong (the representative was a Democrat but the district backed Romney, for example), 20 of the ensuing House races were won by the party whose presidential candidate also won the district. (So in the example in the preceding sentence, the Republicans would gain control of the seat.)

That’s for all six elections, mind you. In the three midterm elections, our numbers had the party of the retiring representative losing eight of the 10 races. (The two exceptions to Wasserman’s rule: The Third Districts in Iowa and New Jersey in 2014, which were held by Republicans despite being won by Barack Obama in 2012.)

Here’s the breakdown by number of seats in each cycle.

Those tall light-blue columns are districts in which the presidential candidate of the retiree’s party won the retiree’s district and then held it after the retiree left office. The dark blue columns, though, are also interesting: Those are races in which the district backed the presidential candidate of the retiree — but then flipped parties in the House race. In other words, it’s the opposite of the Wasserman effect. In our example above, it’s a Republican retiring from a district won by Mitt Romney in 2012 — who then sees a Democrat win the seat. In midterm elections, that happened nine times (out of 105 races in which the retiree’s party won the presidential contest in the district).

If you’re curious, there are four Republicans retiring before 2018 who aren’t seeking a different office and who represent districts won by Hillary Clinton in 2016. There is one Democrat retiring who represents a district won by Donald Trump. (That’s Carol Shea-Porter, whose district has flipped between the parties in every election since 2010.)

The broader point is the one with which we started: There’s a lot of time before the November elections and a lot of time for more retirements, most of which will result in the same party controlling the seat. The interesting — and hard-to-answer — question, of course, is how many won’t.