Sen. John Cornyn is going on offense against Texas Attorney General Ken Paxton as they fight for a Republican Senate runoff, and President Donald Trump’s endorsement hangs over it all. On Thursday, Cornyn’s campaign is releasing a new video that highlights corruption and personal allegations against Paxton. The video revisits Paxton’s impeachment trial and a securities fraud case. On Wednesday, Trump said he plans to endorse one of them before the May 26 runoff and expects the other candidate to quit. Paxton says he'll stay in the race even if Trump picks Cornyn. Republican leaders worry that Paxton’s troubles may risk the seat in the fall election.