Senate Democrats’ hopes of keeping their majority after the next election is complicated by a potential wave of retirements in key battleground and Republican-leaning states.

Sen. Debbie Stabenow (Mich.), a member of the Democratic leadership, announced on Thursday that she won’t run again, and all eyes are on Sens. Joe Manchin (D-W.Va.) and Jon Tester (D-Mont.), who haven’t announced their plans.

Their two seats in reliably Republican presidential states would be particularly difficult to hold on to for Democrats.

“This shapes up to be a very difficult cycle for Democrats anyway and this is just another blow to the chances of keeping the Senate when you lose an incumbent,” Steve Jarding, a Democratic strategist and former advisor to the Democratic Senatorial Campaign Committee, said of Stabenow’s plan to retire.  

Sen. Kyrsten Sinema (Ariz.), who left the Democratic Party to become an Independent, also has not announced her plans. Neither has Sen. Tammy Baldwin (D-Wis.), though she is widely expected to run for re-election. Sen. Sherrod Brown (D-Ohio) is running for reelection, which could help Democrats in that race.

All three represent states where Republicans will like their chances in 2024.

Overall, Senate Democrats need to defend 23 seats in 2024, compared to just 10 for Republicans. All of the GOP incumbents are running in reliably Republican states.  

 Mike Berg, the director of the National Republican Senatorial Committee, says Republicans will “aggressively target” the open Michigan Senate seat, which will force Democrats to play defense in an expensive state.  

“Senate Democrats don’t even have a campaign chair yet and they are already dealing with a major retirement,” Berg said, referring to the Democratic Senate Campaign Committee leadership. “We are going to aggressively target this seat in 2024. This could be the first of many Senate Democrats who decide to retire rather than lose.”

Stabenow is 72 years old but her decision to retire surprised strategists because she is one of Senate Majority Leader Charles Schumer’s (D-N.Y.) closest allies in the Senate Democratic conference and chairs the powerful Agriculture Committee, which is a big selling point in Michigan.

 “It certainly will be competitive,” Matt Grossman, a professor of political science at Michigan State University, said of the race in Michigan. “We’re a swing state and an open Senate race inherently will be competitive in a swing state.” 

He noted that Stabenow beat Republican candidate John James by just more than 6 percentage points in 2018, a year that was a good one for Democrats generally.  

James ran a much closer race in 2020 against Sen. Gary Peters (D-Mich.), who won 49.9 percent to 48.2 percent.  

Howard Edelson, a Democratic strategist with a long history in Michigan politics, said there are a wide array of strong Democrats who could run for Stabenow’s seat, including Whitmer, Michigan Secretary of State Jocelyn Benson and Detroit Mayor Mike Duggan.  

Other names being floated as possible candidates include Reps. Elissa Slotkin (D-Mich.), Debbie Dingell (D-Mich.), Haley Stevens (D-Mich.), Rashida Tlaib (D-Mich.), former Rep. Andy Levin (D-Mich.) and state Sen. Mallory McMorrow.  

In Wisconsin, Republicans are likely to go after Baldwin after Sen. Ron Johnson’s (R-Wis.) re-election victory in November.

Schumer said last month that he will do everything he can to convince Democratic incumbents to run for re-election, which was a big reason why Democrats kept control of the Senate majority despite predictions in 2021 and early 2022 of a Republican midterm election wave.  

“They’re great candidates and we’ll do everything we can to help them,” he said, praising Manchin and Sinema as “great members of our caucus” and “tremendous contributors” even though they “don’t always agree with us on certain issues.”  

The leader noted that “traditionally Democrats do better in a presidential year than a non-presidential year” because Democratic voters, especially young voters, tend to turn out in greater numbers in presidential years.  

But he acknowledged the serious challenges ahead. 

“We have a large number who are up” including “two who are in Trump-, Republican-leaning states,” he said referring to Tester and Manchin.  

Matt House, a Democratic strategist, said Schumer’s best argument for convincing Manchin, Tester and Sinema to run again is to point to the impressive list of legislative accomplishments they racked up in the last Congress.  

He said that is “all the Democratic leaders in the Senate can do from a legislative standpoint to convince them it’s an attractive job and an important role to play.” 

“There are a lot of other forces at play. What’s happening on the Republican side in each of those states, what’s happening at the presidential level, what’s the overall atmospherics of the generic ballot is going to influence their thinking,” he added.  

Senate Republicans say the new chairman of the NRSC, Sen. Steve Daines (R-Mont.), will make an all-out push to flip Tester’s seat and is well positioned to do so given his knowledge of his home state’s politics. 

Tester is on the fence about running again but expressed confidence he could win a fourth term in a state that Trump won by 16 points in 2020.  

He said he needs “to sit down and visit like we have other time” with his family, friends and supporters about running again.  

“I’m getting older, we need to talk about it,” he said. 

Tester said “you can look at the last election and say Jeez it’s trending red” but he said that local Democrats could have made some better decisions to run more competitively in Montana.

“The issues are there. It’s putting in the shoe leather,” he said. “Trust me, I’ve had tough elections before. If I run, this is going to be a tough election again. I have no doubt I can win it …. The truth is I have a good record to run on.”  

Democratic strategists say the party has an outside chance of winning the Montana Senate seat if Tester, who is 66 years old, retires but virtually no shot of keeping Manchin’s seat in West Virginia if he decides not to run for a fourth term.  

Manchin told The Hill last year that he’s still weighing what to do in 2024 but doesn’t plan to make anyone announcement anytime soon.  

Manchin said he’s expecting “rigorous” competition if he runs again, and said he’s “going to put myself in a position to help my state and my country the best I possibly can.”  

Sinema could face a tough three-way race in the general election after announcing her decision to leave the Democratic Party and register as an independent.  

Rep. Ruben Gallego (D-Ariz.) is moving aggressively to position himself for the Democratic Senate nomination. He announced Thursday that he is hiring two fundraising strategists who played key roles on Sen. Mark Kelly’s (D-Ariz.) successful 2022 re-election campaign.