The retirement of Rep. Dave Reichert (R, WA-8) on Wednesday from a swing district immediately transforms that district from a longshot Democratic pickup opportunity to one of their best chances to flip a GOP-held seat in the whole country. Accordingly, we’re moving it from Likely Republican all the way to Toss-up.

Reichert, a former King County (Seattle) sheriff, was first elected in 2004, and despite being a top Democratic target in the 2006 and 2008 wave years, held on each time (even as Barack Obama was winning the district by 15 points in his initial election). Reichert became entrenched after redistricting made WA-8, which includes suburbs of Seattle and Tacoma, more Republican, and at the presidential level it now votes quite similarly to the national average: Hillary Clinton won it by three points last year while carrying the national popular vote by two.

A key factor in a potential Democratic House takeover next year is how many, and which, Republicans decide not to run for reelection next year. Taking over open seats is easier than defeating incumbents, and a Crystal Ball analysis recently found that the president’s party often sees a giant drop in midterm performance in open seats from the previous incumbent’s showing two years prior. On average over the last three midterms (2006, 2010, and 2014, all wave years for one party or the other), the president’s party lost a whopping 22 points in margin in open seats they were defending in the midterm. Repeating that 22-point average drop in presidential party performance would flip WA-8 from red to blue despite Reichert’s easy 20-point victory in 2016.

If one would have asked Democrats at the start of the year to pick two, but only two, House Republicans to retire in advance of 2018, they might have easily picked Reichert and Rep. Ileana Ros-Lehtinen (R, FL-27), who holds a seat Clinton won by 20 points and where we have installed the Democrats as early favorites after Ros-Lehtinen’s retirement. Had they been running for reelection, Reichert and Ros-Lehtinen may have been close to unbeatable even in a Democratic wave environment; now Democrats have, probably at worst, even odds to win both seats.

While one could argue that WA-8, like FL-27, should be Leans Democratic as well, we’re being a little cautious in the Evergreen State seat. For one thing, it’s unclear who the candidates will be. Democrats already have a large field of at least five credible candidates, and others may enter now that Reichert is gone. The Republicans may turn to state Sen. Dino Rossi (R), who lost close statewide races in 2004, 2008, and 2010. One potential problem for Democrats is that Washington, like California, is a top-two primary state, meaning that all candidates run together in the primary and the top two finishers advance to the general election. It’s possible that if there are several Democrats running and just two credible Republicans, the GOP could squeeze two candidates into the general election and shut out the Democrats.

So we’ll just have to wait and see — both for how the field in this newly-open seat develops, and whether other Republicans from marginal districts opt against running again in 2018. A few more Republican retirements in districts like WA-8 (and FL-27) would make a Democratic House takeover even more plausible than it already is based on President Trump’s currently poor approval numbers, the Democratic lead in the House generic ballot polling, and the frequently poor performances for the president’s party in midterms more generally.

Table 1: Crystal Ball House ratings change