But after trailing in the primary contest for months, Mr. Vance enters the final stretch as something of a front-runner, with the other candidates training their fire on him.
Providing air cover for Mr. Mandel, the business-backed political action committee the Club for Growth is broadcasting an advertisement repeating attacks that Mr. Vance made in 2016 against Mr. Trump and his supporters, suggesting the former president made a mistake with his endorsement.
A pro-Vance super PAC, heavily funded by Peter Thiel, the Trump-aligned financier that Mr. Vance works for, fired back Friday with an ad running in Columbus, Dayton and Cleveland that portrays Mr. Mandel as a “squish.” Mr. Mandel’s embrace by the Republican nominees for the presidency in 2008 and 2012, John McCain and Mitt Romney, are treated in the advertisement like a scarlet letter, and kind words from Mr. Kasich might as well have come from Nancy Pelosi.
“Josh Mandel, he’s for them, not us,” the narrator intones, a clear message that Tuesday’s primary is geared toward the Republican extremes, not the sort of voters who once backed Mr. Kasich and Mr. Romney.
Mr. Gibbons, still in the hunt for the nomination, will trot out yet another Trump ally, Senator Rand Paul of Kentucky, on Monday to attest to his conservative bona fides. In a series of statements on Friday seemingly issued to appeal to the far right, Mr. Gibbons declared that a “dire need of real change” meant he would support a convention to rewrite the Constitution, and said that a new effort by the Department of Homeland Security to combat disinformation would be “a de facto ‘Ministry of Truth’” to crush dissent.
Jonathan Weisman reported from Columbus, Ohio, and Trip Gabriel from Dayton. Shane Goldmacher and Maggie Haberman contributed reporting.