President Donald Trump is threatening to cancel the May 26 Texas Republican Senate runoff between incumbent Sen. John Cornyn and Texas Attorney General Ken Paxton, demanding the race stop immediately. After neither candidate secured 50 percent in Tuesday's primary, a runoff became necessary. Trump, who didn't initially endorse either candidate, posted that the race "cannot be allowed to go on any longer" and "must stop now." He promised an endorsement conditional on the losing candidate immediat...