Rep. Sean Duffy (R-WI) has abruptly decided to resign from Congress, according to Politco reporter Jake Sherman.

Duffy, a staunch conservative who has been one of President Donald Trump’s biggest supporters, represents a Republican-leaning district that Cook Political Report rates as tilted seven points toward the GOP.

Despite the “blue wave” that helped Democrats retake Congress in 2018, Duffy won his reelection race easily and defeated Democratic challenger Margaret Engebretson by more than 20 points.