Republican primary voters on Tuesday rejected U.S. Sen. John Cornyn, one of the Senate's most senior GOP members, in favor of Trump-backed Texas Attorney General Ken Paxton. Why it matters: Cornyn's loss marks one of the most significant defeats for a Republican senator in years and underscores how loyalty to President Trump continues to reshape GOP primaries nationwide. Trump gave Paxton a last-minute endorsement in the runoff. What they're saying: "Tonight is the beginning of the fight to pr