GRAND RAPIDS, Mich. (AP) — Outgoing Michigan Sen. Gary Peters is endorsing U.S. Rep. Haley Stevens as his successor, adding to a growing effort by the Democratic establishment to help her defeat progressive favorite Abdul El-Sayed in next month’s primary.

Peters, who is retiring after 12 years in the Senate, said Stevens “will be ready on day one to fight for Michigan.” The endorsement, which was announced Monday, marks a reversal for Peters, who told The Associated Press in late May that he intended to stay neutral in the race.

But since then, Democratic leaders have increasingly rallied behind Stevens as the Aug. 4 primary approaches and concerns grow that El-Sayed is too far left to succeed in November. Holding the Michigan seat is viewed as critical to Democrats’ hopes of reclaiming the Senate majority.

Stevens, a four-term House member, has campaigned as a more moderate Democrat focused on manufacturing issues in the critical battleground state. El-Sayed, who has never held elected office, is running on a more progressive platform that includes Medicare for All and campaign finance reform. He’s also been outspoken about the war in Gaza, which has been a fault line within the party.

Concerns about Michigan have only intensified after Democrats’ attempt to flip a Senate seat in Maine was thrown into turmoil when nominee Graham Platner withdrew from the race following a sexual assault allegation last week. Democrats there must now choose a new nominee to face Republican Sen. Susan Collins.

Peters’ endorsement also comes after state Sen. Mallory McMorrow dropped out of Michigan’s Democratic primary earlier this month, transforming the race into a head-to-head contest between Stevens and El-Sayed.

“Senator Peters knows what it takes to win in Michigan, and he knows what Michigan needs from our next U.S. Senator: grit, effectiveness, hard work, and Michigan common sense,” Stevens said in a statement. “I am honored to have his support.”

Peters won two Senate races in Michigan and led Senate Democrats’ campaign arm during the 2022 and 2024 election cycles.

His endorsement adds to Stevens’ growing support from the Democratic establishment, with the race being viewed nationally as a broader fight over the party’s direction.

Senate Democratic leader Chuck Schumer of New York has also backed Stevens, along with Sen. Ruben Gallego of Arizona and Sen. Catherine Cortez Masto of Nevada. El-Sayed has support from Sen. Bernie Sanders of Vermont and, more recently, Sen. Chris Van Hollen of Maryland.

The campaign has grown increasingly contentious in recent weeks.

El-Sayed has attacked Stevens over tens of millions of dollars in outside spending supporting her campaign, including by the American Israel Public Affairs Committee. Stevens has criticized El-Sayed for not disclosing his personal financial records.

During a July 7 debate, each accused the other of running a negative campaign.

“Abdul has spent this entire campaign attacking me,” Stevens said.

The Democratic winner will likely face Republican Mike Rogers, a former member of the U.S. House running uncontested for his party’s nomination, in what is expected to be one of the country’s most expensive and closely watched Senate races.

Joey Cappelletti, The Associated Press