California Democratic Sen. Dianne Feinstein ended months of speculation Tuesday, announcing she wouldn't run for re-election.
While the decision had been expected, the announcement from the 89-year-old was one of the big political questions shaping the 2024 Senate map, with a crowded field already forming well before Feinstein's announcement.
Here are some of the key senators who still haven't made their 2024 intentions official:
Arizona Independent Sen. Kyrsten Sinema
Sinema's decision to leave the Democratic Party has stoked many questions about her political future, both about whether she intends to run again and what the possible presence of an independent incumbent could mean for the two parties.
The senator didn't reveal her 2024 intentions when Rep. Ruben Gallego, D-Ariz., announced his Senate bid. And it remains to be seen whether she'll run.
Montana Democratic Sen. Jon Tester
Battle-tested in a state then-President Donald Trump won by about 16 points, Tester is a key candidate for Democrats as they look to maintain their slim edge in the Senate.
Tester recently told NBC News' Sahil Kapur he hadn't decided whether he'll run again, saying: "I've got a few things to think about" and adding that he also has to take care of the farm that's "been in the family for over 100 years."
"We got to make sure that’s taken care of. We got to make sure that we’ve thought through all the procedures of what’s going to happen over the next eight years. And so once we get through with that, then we can come down and make a decision," he added.
West Virginia Democratic Sen. Joe Manchin
Democrats face a similar dynamic in West Virginia, a state Trump won in 2020 by almost 40 points.
And Manchin was similarly non-committal in an interview with Kapur, even as Republican Gov. Jim Justice publicly weighs a bid.
“Who knows?” he said. “Our primary is not until May of 2024. And there’s nobody wanting in the wings or champing at the bit.”
Pennsylvania Democratic Sen. Bob Casey
The Keystone State is fresh off one of the most heated Senate races of the 2022 calendar and will likely be home to another hotly contested race next year.
Casey, 62, has served three terms in the Senate and had been seen as likely to run for a fourth. But after his announcement earlier this year that he had been diagnosed with prostate cancer, a spokeswoman declined to say whether he would run in 2024.
Vermont Independent Sen. Bernie Sanders
Sanders, who caucuses with Democrats, recently told the New York Times that he would not run for president again if President Joe Biden runs for re-election, but he also would not tell the Times if he plans to run for re-election to the Senate.
Sanders, who can influence domestic policy as chairman of the Senate Health, Education, Labor and Pensions Committee, was first elected to the Senate in 2006 after serving in the House.
While Democrats would be favored to hold onto Sanders' Senate seat if he decides to retire, the state did just re-elect GOP Gov. Phil Scott by 47 percentage points.