For the first time since 2010, an American man has made to the Australian Open quarterfinals. The aptly named Tennys Sandgren is the last American standing in the men’s singles division, an achievement that is ever-so-slightly tainted by the fact that he’s probably a huge Trump supporter — and not the craven “Trump is terrible but I voted for him anyway because I am a Republican” kind, but the out-and-proud MAGA hat-wearing, “Pizzagate is real” kind. At a post-match press conference on Monday, a reporter asked Sandgren about his Twitter account, where he’s retweeted and engaged in conversation with prominent...