Sen. Dick Durbin (D-IL), the Senate Democratic whip, announced on Wednesday that he will not seek reelection to a sixth term, setting up a competitive primary contest to fill his seat and his leadership role. 

Durbin, 80, the second highest ranking member of his conference and the top Democrat on the Senate Judiciary Committee, is the fifth Senate Democrat to retire this year, joining Sens. Gary Peters (D-MI), Tina Smith (D-MN), Jeanne Shaheen (D-NH) and Michael Bennet (D-CO).

“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. So, I am announcing today that I will not be seeking re-election at the end of my term,” Durbin said in a statement and video posted to social media. 

Durbin, who was first elected to Congress in 1982 as a stalwart supporter of Israel, has grown more critical of the Jewish state in recent years. He joined the left-wing faction of his party that supported Sen. Bernie Sanders’ (I-VT) resolutions to cut off some arms sales to Israel over the last year. He also drew criticism for sidestepping the fight against antisemitism, avoiding holding Senate Judiciary Committee hearings that focused on the plight of Jewish students facing discrimination on campuses. 

The news of Durbin’s decision to step aside sets up several contests to replace him, both for his Senate seat and in his several leadership positions in the Senate Democratic Conference. 

Sens. Cory Booker (D-NJ) and Brian Schatz (D-HI) are among the names being floated for Durbin’s whip role. Others in leadership who could be interested include Sens. Amy Klobuchar (D-MN), Tammy Baldwin (D-WI), Catherine Cortez Masto (D-NV) and Chris Murphy (D-CT), all of whom currently serve in leadership.

Sen. Sheldon Whitehouse (D-RI) is the top contender to succeed Durbin as the ranking Democrat on the Judiciary Committee. Whitehouse is currently the No. 2 Democrat on the committee, and has previously challenged Durbin for the top spot. 

While Illinois is a solidly Democratic state, the battle to succeed him is likely to expose divisions within the Democratic Party between moderates and progressives, and potentially showcase the fractures over Israel within the party.

Rep. Raja Krishnamoorthi (D-IL), a top fundraiser and pragmatic lawmaker, is viewed as a leading candidate for the seat. Rep. Lauren Underwood (D-IL), Rep. Robin Kelly (D-IL) and Illinois Lt. Gov. Juliana Stratton have also been named in news reports as potential candidates.