LANSING, Mich. (AP) — Michigan Sen. Debbie Stabenow, a member of the Democratic leadership, announced Thursday that she will not run for a fifth term in 2024, a surprise decision that sets up a scramble by both parties for an open seat in the key battleground state. “It really was the right time for me,” she said.

The news shocked many Democrats in the state and her impending retirement turns Michigan’s next Senate race into one of the most competitive in the country as the party tries to preserve its slim majority.

Stabenow told The Associated Press that she made the decision to retire a few months ago. “I knew that this was a moment when I could pass the torch to the next generation of leaders,” she said.

Democrats will face a test to find a candidate with Stabenow’s broad support. “We’ll see how things develop,” the senator said, adding that she expects “to have a lot of discussions with people.”

On the GOP side, the National Republican Senatorial Committee, which works to elect Republicans, said in a statement after Stabenow’s announcement that it would “aggressively target this seat in 2024.”

While the current political climate in Michigan favors Democrats following a midterm election where they flipped the state House and Senate, the state is still expected to be one of the nation’s premier battlegrounds in the 2024 presidential election. Only one Michigan Republican has held a seat in the Senate in the past 40 years.

Among the Democrats whose names began circulating after Stabenow’s announcement are Pete Buttigieg, the federal transportation secretary who ran for president in 2020 and moved from Indiana to northern Michigan last year to be closer to his husband’s family; Elissa Slotkin, a congresswoman first elected in 2018 and coming off a decisive victory in November in one of the country’s most competitive House districts; and state Sen. Mallory McMorrow, who has seen her profile rise since going viral with a speech denouncing Republicans over “grooming” accusations.

Buttigieg said in a statement that he was “fully focused” on his Cabinet post and was “not seeking any other job.”

Democratic Gov. Gretchen Whitmer, who has been mentioned as a possible future White House candidate and was just sworn in Sunday for a second term, issued a statement in which she ruled out a potential Senate run and reaffirmed that she would stay in office for the next four years.

On the Republican side, names that surfaced include John James, who was elected to Congress in November after losing Senate races to Stabenow in 2018 and Democrat Gary Peters in 2020; Tom Barrett, a former state representative defeated by Slotkin last year; and former Rep. Fred Upton, the longest-serving member of the congressional delegation before he decided not to run in 2022 after voting to impeach then-President Donald Trump over the Capitol riot.

Republican Tudor Dixon, who lost to Whitmer in 2022, is not ruling out a run for Senate, according to spokeswoman Sara Broadwater.

Stabenow joined Congress in 1996 after serving in the Michigan Legislature. In 2000, she made history by becoming the first woman to be elected senator in Michigan, defeating one-term Republican Sen. Spence Abraham. She turned back GOP challenges in 2006 and 2012 and defeated James by 6.5 percentage points in her last election in 2018.

Stabenow is the longest-serving member of the state’s congressional delegation. She is chair of the Democratic Policy and Communications Committee, making her the No. 3 ranking party leader, and heads the Senate Agriculture, Nutrition and Forestry Committee.

Stabenow most recently has been involved in bipartisan legislation aimed at increasing oversight of cryptocurrencies. She has also led efforts to expand and increase funding for mental health care both nationally and in Michigan.

Praise for Stabenow began pouring in after her retirement announcement. Stabenow said she heard from President Joe Biden with a “call of support and commitment to work together in the next two years.”

Democratic Gary Peters, the state’s junior senator who has served with Stabenow since 2015, said she would leave a legacy “as a champion for children, women and families, workers, manufacturing and our auto industry, mental health care and the Great Lakes.”

Buttigieg said Stabenow was “a force in the Senate” while McMorrow called her a “trailblazer.”

“No one has been more instrumental in building the infrastructure of the Michigan Democratic Party to this historic moment we’re in today,” McMorrow said.