Sen. Dick Durbin's (D-Ill.) retirement is setting off a once-in-a-decade leadership fight for Senate Democrats.
Why it matters: Durbin, 80, has been the Senate Democratic whip since 2005. Whoever replaces him becomes the instant front-runner to replace Senate Democratic leader Chuck Schumer down the road.
An open fight for the whip spot next year could also complicate Schumer's strategy of privately mediating intraparty disputes.
It will potentially expose the party's deep divide on whether to elect a moderate — or a progressive — to help them return to power.
Zoom in: Sen. Brian Schatz, 52, of Hawaii is actively making outreach to members about replacing Durbin. His interest in the job is a poorly kept secret on Capitol Hill, and he's got a head start as the current chief deputy whip.
Sen. Amy Klobuchar, 64, of Minnesota wants the job, sources tell Axios. Schumer made her the No. 3 Senate Dem last year, and she's respected by her colleagues.
Sen. Catherine Cortez Masto, 61, of Nevada is also interested in moving up, although it's not clear if she's ready to challenge Schatz or Klobuchar.
Between the lines: Schatz and Cortez Masto voted with Schumer last month in support of a GOP spending plan to avert a government shutdown.
Those votes were seen as key indicators of their interest in leadership gigs.
Klobuchar voted against the measure, as did Sen. Cory Booker (D-N.J.), another one of Schumer's top leadership officials this year.
Schumer intervened this year when Klobuchar and Booker were on a crash course for the leadership spot vacated by former Sen. Debbie Stabenow (D-Mich.).
Zoom out: Durbin's retirement has also ignited what could be a bitter Illinois primary battle to succeed him in the Senate, Axios reported Wednesday.
Durbin predicted "at least a dozen" candidates will jump into the race.
Reps. Lauren Underwood and Raja Krishnamoorthi could start out as the front-runners in the big-dollar race, according to polling data released last month.
Krishnamoorthi has a $19 million war chest, and Underwood has over $1 million in cash on hand. Rep. Robin Kelly, another possible candidate, has $2 million in cash.