President Donald Trump has endorsed Texas Attorney General Ken Paxton, supercharging his effort to oust incumbent Sen. John Cornyn in a Republican primary runoff. Paxton and Cornyn qualified for the May 26 runoff after a March 3 primary. Trump wrote on social media that Paxton is “a true MAGA Warrior.” Although the four-term Cornyn has backed Trump’s agenda in Washington, Paxton pitched himself as a political warrior for the Make America Great Again movement. Trump’s endorsement Tuesday puts him at odds with his party’s establishment, which is convinced Cornyn is the better candidate for November’s general election. The runoff had been shaping up as a bitter and expensive battle for the future of the Republican Party.