Dick Durbin, the Senate’s longtime second-ranking Democrat, announced plans to retire at the end of next year, sparking a succession scramble to fill his powerful leadership position in the chamber, as well as a crowded primary in Illinois.

Durbin, 80, had long been expected to retire, having served in the chamber since 1996 and as the Senate Democratic whip since 2005, a position that gave him clout with the party’s leader as chief deputy to the late Harry Reid and now with Senate Democratic Leader Chuck Schumer.

Durbin becomes the fourth Senate Democrat to announce his retirement rather than seek reelection next year.

“The decision of whether to run for re-election has not been easy. I truly love the job of being a United States Senator. But in my heart, I know it’s time to pass the torch,” Durbin announced Wednesday. “So, I am announcing today that I will not be seeking re-election at the end of my term.”

Durbin’s retirement decision opens up several key positions, including chairman of the Senate Judiciary Committee in the previous Congress, where he presided over the confirmation of Ketanji Brown Jackson, the first Black woman to serve on the Supreme Court, and where he has long advocated for legislation to assist Dreamers, undocumented migrants brought to the United States as children.