Five and a half months ago, a triumphant Ken Paxton took the microphone at a Tex-Mex restaurant in Collin County, his political home base, with major news: He had spoken with President Donald Trump earlier that day, and Trump’s long-awaited endorsement had arrived. Paxton celebrated with an exuberant crowd of supporters, days ahead of his Trump-fueled shellacking of Sen. John Cornyn in the Republican primary runoff.