When a political player starts drawing personal insults from President Trump and his people, it is a pretty good sign that his star is on the rise. For Senator Jon Ossoff of Georgia, that moment arrived this summer. In July, Mr. Trump dubbed the fresh-faced lawmaker “Pee-wee Herman.” The next month, upset over Mr. Ossoff’s criticism of the president, one aide called Mr. Ossoff a “feminine theater kid” and a “lightweight loser,” and another derided him as “a miserable person” and “the biggest cuck loser in politics,” while deploying a sexually explicit moniker unfit for a family-friendly publication. Mr. Ossoff...