The senior senator of Ohio, Sherrod Brown, is up for reelection next year in a high-profile race, but unlike vulnerable Democrats in 2022, he can’t count on President Trump elevating a primary candidate who goes on to lose on Election Day. Mr. Brown’s junior colleague, Senator Vance, is proof that the former president’s brand remains strong in the Buckeye State.

In 2020, Mr. Trump won Ohio by 8.3 points, maintaining his exact margin of victory in 2016, even as he saw an erosion of support elsewhere. That allowed President Biden to flip Michigan, Wisconsin, Arizona, and Pennsylvania to win the White House.

Mr. Trump often boasts of his endorsements securing victory, but in last year’s midterms, Democrats bet against his Midas Touch with a high-risk and expensive strategy. They spent $53 million to boost so-called “MAGA Republicans” in 13 GOP primaries. All eight candidates who won their party’s nomination went on to lose the general election.

The play may well have gained Democrats control of the Senate. In New Hampshire, as I wrote in the Sun, a PAC allied with Majority Leader Schumer gave New Hampshire’s GOP candidate, General Donald Bolduc, a $3.2 million infusion of cash. It made a huge difference in a primary decided by just 2,000 votes.

General Bolduc beat a more moderate Republican backed by Governor Chris Sununu, the son of an establishment Republican, Governor John Sununu, who served as White House chief of staff for President George H. W. Bush. General Bolduc lost to Senator Hassan, whom the Boston Globe had described as “the most vulnerable Senate Democrat.”

In 2024, Ohio is one of three states that had a Senate contest and that Mr. Trump won in 2020.  The others were Montana and Ohio’s neighbor, West Virginia. Last year, Mr. Vance held a seat in Ohio for Republicans. That was after the retirement of Senator Portman. Mr. Vance ran an outsider campaign as the author of the best-selling memoir, “Hillbilly Elegy.”

Of the six Senate candidates Mr. Trump endorsed in the midterm primaries, three won, but Senator Johnson of Wisconsin was an incumbent and Senator Budd of North Carolina moved up from the House. The four others were political newcomers; of these, only Mr. Vance triumphed, crushing his opponent, Congressman Tim Ryan, by more than six points.

Three Republicans are running for Ohio’s 2024 Senate nomination. A state senator and critic of Mr. Trump, Matt Dolan, and the secretary of state, Frank LaRose — who earned Mr. Trump’s endorsement in his 2022 race — already hold public office. Mr. Vance believes “the man for the job” is a fellow outsider, Bernie Moreno. Described by the Cincinnati Enquirer as a “luxury car dealer turned blockchain executive,” Mr. Moreno is the previous owner of 15 car dealerships and other businesses including a tech company.

“This seat,” a representative for Mr. Vance tells me, “needs to go to a conservative dedicated to making Ohio’s working and middle-class families heard, fighting for America First policies that make our country great — someone who is tough on China, knows firsthand the importance of settling in this country legally, and who will fight the woke corporations and Big Tech that try to censor conservatives.”

The National Republican Senatorial Committee, like Mr. Trump for now, is staying out of the primary. “When you have three candidates that any one of them could win the general election,” the GOP committee chairman, Senator Daines of Montana, told CBS last week, “we don’t stay up late at night worrying about that.”

For his part, Mr. Moreno is campaigning in Mr. Trump’s mold. His spokesman, Conor McGuinness, tells the Daily Beast that Messrs. Dolan and LaRose “are career politicians and liberal Republicans who don’t have the courage to stand up to the D.C. swamp.”

Although Mr. Trump hasn’t backed a candidate, he did encourage Mr. Moreno’s run. Mr. Trump, in a post on Truth Social, calls him a “highly respected businessman.” He says that Mr. Moreno “would not be easy to beat, especially against Brown, one of the worst in the Senate.”

With Mr. Trump’s power as a kingmaker, he could decide the winner of Ohio’s Republican primary on March 19. If he does make an endorsement, Mr. Brown will have a fight on his hands, with Ohio promising to be a place where Democrats have to work to win rather than sit back and wait for MAGA candidates to lose.