Of all the issues defining the U.S. Senate race between Republican Mehmet Oz and Democrat John Fetterman, Mr. Fetterman’s health should rank close to last. Even so, it has loomed large in an increasingly tight contest for a potentially pivotal U.S. Senate seat. Mr. Fetterman can diminish the influence of this distracting side-issue by releasing his medical records now and allowing reporters to question his physician. In September, a Post-Gazette editorial called on both U.S. Senate nominees to release their medical records. Mr. Oz, 62, released his two days later, indicating he was in good health. Mr. Fetterman, 53, who...