A new poll shows Donald Trump-endorsed former U.S. Rep. Mike Rogers leading the Republican primary for the U.S. Senate seat vacated by Sen. Debbie Stabenow, though more than half surveyed remain undecided.

“With over three months to go until the August Michigan Senate primary, a majority of Republican primary voters are undecided; Trump-endorsed Mike Rogers has the most support among the group of candidates at 32%,” said Spencer Kimball, executive director of Emerson College Polling. “Rogers’ support is ten points higher among male voters than female, 37% to 27%, and among voters with a college degree than those without, 38% to 29%.”

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The poll of 545 likely Republican primary voters conducted Tuesday and Wednesday found 54% remain undecided, 32% back Rogers, and 8% support former U.S. Rep. Justin Amash. Another 3% back businessman Sandy Pensler, and 2% plan to vote for Sherry O’Donnell, a physician and former U.S. congressional candidate.

Those polled also had a more favorable view of Rogers than the others, with 59% reporting a very or somewhat favorable opinion, compared to 32% for Amash, 27% for Pensler, and 19% for O’Donnell.

The Emerson College poll comes just six days after former U.S. Rep. Peter Meijer, who voted to impeach former President Trump, withdrew from the race.

“The hard reality is the fundamentals of the race have changed significantly since we launched this campaign,” Meijer said.

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Meijer’s exit followed about six weeks after Trump endorsed Rogers, a former House Intelligence chairman who left Congress in 2015 after 14 years in the lower chamber.

“Mike has served his Country during a career loaded up with accolades and wins, from the Army to Congress, and now, hopefully the U.S. Senate,” Trump posed to Truth Social. “Mike Rogers will be a Great and Powerful Senator for Michigan, and has my Complete and Total Endorsement. HE KNOWS HOW TO WIN!”

While momentum appears to be in Rogers’ favor, Pensler is pouring money into advertising on TV and online to target Democratic frontrunner U.S. Rep. Elissa Slotkin of Holly and contrast his candidacy with Rogers’.

Pensler senior advisor Stu Sandler told The Detroit News “he’s going to spend a serious amount” throughout the primary to go after both Rogers and Slotkin and build name recognition with voters.

“We’re just going to keep putting them on the air,” Sandler said.

Montana Sen. Steve Daines, chairman of the National Republican Senatorial Committee, told the news site Trump’s endorsement of Rogers “dramatically” shifted polling in his favor.

“I think the Trump endorsement of Mike Rogers really seals the deal in that primary,” he said at a Washington breakfast on Thursday.

Daines and others are expecting Rogers to face off against U.S. Rep. Elissa Slotkin in November, though Slotkin has her own primary challengers. While campaign finance records show Slotkin amassed more than $8 million in cash by the end of March, former Michigan Congressman Fred Upton predicts the “race is going to go down to the wire,” WZZM reports.

“This is going to be two heavyweights, in a positive way,” Upton said. “They really know the issues and will go toe to toe with them.”

Rogers told WZZM he’s not concerned with Slotkin’s fundraising outpacing his own 4-1.

“We’re going to run a better campaign. We don’t have to match dollar for dollar,” he said. “All we’ve got to do is have enough money to make sure people understand the differences.”