Rep. Dave Trott of Michigan has declined to seek re-election, putting another swing district in play for next year, and creating another headache for Paul Ryan.

Historically, it is bad news for a political party when incumbents in their House majority, particularly those in swing districts, start retiring en masse.

2006 and 2010, wave elections that flipped control of the House, were both foreshadowed by a slew of Republican and Democratic retirements, respectively.

Now, the same early warning signs are brewing for House Speaker Paul Ryan and his GOP majority, after no fewer than three members of Ryan’s caucus announced their retirement in just the past seven days.

Last week, two “moderate” Republicans, Rep. Dave Reichert of Washington and Rep. Charlie Dent of Pennsylvania, declared they were out for 2018. Both are suspected to have announced their retirement partly due to Trump, and in his resignation speech, Dent explicitly complained that “the most basic tasks of governing” had become nearly impossible.

And Monday, Rep. Dave Trott of Michigan followed suit after only two terms in office:

Trott’s congressional district, Michigan’s 11th, encompasses the northwest suburbs of Detroit. It is right-leaning, but not by much — voters there backed Trump and Romney by a margin of 5 points each. It is exactly the kind of district that Republicans could easily hold onto with an established incumbent like Trott, but would be up for grabs as an open seat in a wave election year.

If Democrats field a candidate in this district who not only capitalizes on anti-Trump anger but also champions the Democratic Party’s positive platform of economic justice for working families, this seat is easily within reach.

As the midterms and other state elections draw closer, Democrats have a new window to campaign on positive change and against Trump’s right-wing agenda — and Republicans know it.