Republican Ken Paxton's 28-point primary rout of longtime Texas Sen. John Cornyn — the widest primary defeat for a sitting U.S. senator in nearly 50 years — further cements President Trump's hold on the GOP — but may complicate the party's ability to protect its Senate majority in November. Why it matters: As election returns rolled in late Tuesday, top Republicans stewed over Trump's endorsement of Paxton — Texas' attorney general with a long history of legal and ethical troubles who they belie