Sen. Dick Durbin speaks at a press conference at the U.S. Capitol on March 4. Photo: ALLISON ROBBERT/AFP via Getty Images

Sen. Dick Durbin‘s (D-Ill.) announcement Wednesday that he is retiring rather than running for reelection in 2026 is likely to set off a fierce Democratic primary for his seat.

Why it matters: Durbin himself predicts that “at least a dozen” candidates will jump into the race, with at least three House Democrats and the state’s lieutenant governor all eyeing bids.

• Reps. Lauren Underwood and Raja Krishnamoorthi could start out as the frontrunners, according to polling data released last month.
• The race could quickly get expensive: Krishnamoorthi has amassed a $19 million war chest, and Underwood has over $1 million in cash on hand. Rep. Robin Kelly also has $2 million in cash.

Driving the news: “The decision of whether to run for reelection 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, 80, said in a video.

• The Senate minority whip and Judiciary Committee ranking member said he “will not be seeking reelection at the end of my term.”
• Durbin is not immediately endorsing a potential successor, but he did not rule out throwing his weight behind someone in the future, according to the Chicago Sun Times.

What we’re hearing: Underwood is widely expected to jump into the race, with one source familiar with the matter telling Axios the writing is on the wall and that it’s just a matter of “when” and not “if.”

• A House Democrat, speaking on the condition of anonymity, told Axios: “I think Raja Krishnamoorthi is going to run.”
• Kelly, the former chair of the Illinois Democratic Party, has also been looking at a run, as Axios previously reported. So has Lt. Gov. Juliana Stratton.

Zoom out: The primary could be an expensive headache for Senate Democrats at a time when they are already dealing with several other possible slugfests.

• Rep. Haley Stevens on Tuesday jumped into the race for retiring Michigan Sen. Gary Peters’ seat and will face off against state Sen. Mallory McMorrow and Dr. Abdul El-Sayed.
• Rep. Angie Craig is also expected to run against Minnesota Lt. Gov. Peggy Flanagan for retiring Sen. Tina Smith’s seat.
• Senate Democrats also hope to get former North Carolina Gov. Roy Cooper to run for Senate even as former Rep. Wiley Nickel is already in the race.

Editor’s note: This story has been updated with additional reporting.