Texas Attorney General Ken Paxton’s decision to challenge Sen. John Cornyn sets up what’s likely to be a bitter and expensive Republican primary – and a battle for President Donald Trump’s endorsement.

Texas Attorney General Ken Paxton has told Newsweek he is launching a primary challenge to fellow Republican and incumbent Senator John Cornyn, accusing him of "turning his back on President Trump and the America First agenda.

Texas Attorney General Ken Paxton on Tuesday night announced a primary challenge against longtime Sen. John Cornyn, setting the stage for a battle between two politicians representing different parts of the Republican Party.