“I’m thankful for my health” is a common refrain heard around the Thanksgiving table. But for Pennsylvania’s John Fetterman, the feeling is a bit more complicated. David J. Garrow reviews the senator’s frank memoir, Unfettered. “An October 25 debate against Oz was a disaster. ‘My nerves beat me down. I had wilted. I’d choked,’ and in its wake ‘I had mentally collapsed.’ Now ‘I never thought I would win’ the race to become a senator, which felt all well and good since ‘I didn’t deserve to be one.’ But win Fetterman did, by a margin of more than 250,000 votes,...