“I’ll make that decision after the 1st of the year,” he said in a brief interview Tuesday.

Durbin is not up for reelection until 2026, but his retirement would have monumental implications for both Illinois politics and the makeup of Democratic leadership.

At age 79, he has served in the Senate since 1997 and would be 88 at the end of a sixth term.

Durbin quickly rose through the ranks of leadership, attaining the No. 2 position of whip in 2005. Any vacancy would set in motion the biggest leadership race for the party since Leader Harry Reid announced his retirement in 2015.

Several Illinois Democrats have been floated as successors for the Senate seat itself, including Illinois Attorney General Kwame Raoul and House Reps. Raja Krishnamoorthi (D-IL) and Lauren Underwood (D-IL).

The state’s other senator, Tammy Duckworth (D-IL), is 56, meaning it could be years or decades before another Senate vacancy arises.

On the GOP side, Rep. Darrin LaHood (R-IL) has been mentioned as a contender for the seat. A Republican has not been elected to the Senate in Illinois since 2010.

Durbin, who has undergone several medical procedures in recent years, has previously said he is mindful of his “physical and mental abilities” when weighing whether to run for reelection.

He underwent a hip surgery in June and, months earlier, had his knee replaced. In 2017, he underwent an outpatient procedure to address an abnormal heart rhythm.

Durbin’s decision comes as Republicans weigh who will replace Sen. Mitch McConnell (R-KY), the longest-serving party leader in Senate history. McConnell, 82, announced his retirement from leadership in February, though he will serve out the remainder of his term through 2026.