GOP Sen. John Boozman (Ark.) voted with former President Trump more than 91 percent of the time and snapped up an early 2022 endorsement and a donation from his PAC. But as Boozman seeks a third term for his reliably red Senate seat, his primary opponents are coming after him by trying to paint themselves, and not the 71-year-old, as the real Trump candidate. The under-the-radar race has echoes of the broader headaches facing Republicans heading into primaries: anti-establishment challengers trying to claim the former president’s mantle, and his voter base, while they face off with traditionally conservative — and...