Still, while Mr. Trump’s endorsement made the critical difference, only 1 of 11 Ohio Republicans followed Mr. Trump’s call to fall in line as Mr. Vance’s share grew from 23% in the last pre-endorsement poll to 32% on Election Day. His 9% bump was overshadowed by the rise of Mr. Dolan, who nearly doubled his share of the vote after Mr. Trump announced his late-in-the-race endorsement. Almost 68% of Ohio Republicans ignored or rejected the former president’s call to join in his “Complete and Total Endorsement” of Mr. Vance.

It didn’t help that many Trumpers didn’t like Mr. Vance. Ohio Republican county party officials and national convention delegates who were Trump loyalists publicly expressed their displeasure with the former president’s decision.

The gubernatorial primary in Ohio also highlighted the limits of Mr. Trump’s sway. While the former president didn’t endorse any candidate outright in the four-way race, he made it clear that incumbent Gov. Mike DeWine wasn’t a favorite, calling him a “terrible governor” and a “terrible, terrible guy” at an April 23 rally for Mr. Vance. Still, Mr. DeWine was comfortably renominated, proving that candidates can survive a denunciation by the former president.