Republicans running for the seat of Ohio’s retiring senator, Rob Portman, appear determined to bury the soft-spoken country-club bonhomie that was once a hallmark of the party in this state, and replace it with the pugilistic brand of conservatism owned by Donald J. Trump and now amplified by the new band of Buckeye bomb throwers. The race descended into a brutal slugfest as the leading candidates, the author-turned-venture capitalist J.D. Vance, the former state treasurer Josh Mandel and a self-funded businessman, Mike Gibbons, entered the final weekend before Tuesday’s primaries accusing one another of being insufficiently right-wing or disloyal to...