Christian Castro, who had been charged with assault in the shooting of a Venezuelan man during the immigration crackdown in Minnesota, was taken into custody Friday morning.
After attacking the Texas attorney general, who won the G.O.P. nomination, Senate Republicans are pivoting sharply to support him in what is now a competitive race.
Personal attacks and a packed campaign rally set the tone for what is likely to be a rancorous contest in Texas for U.S. Senate between James Talarico and Ken Paxton.
The breadth of Mr. Cornyn’s loss showed the enduring unpopularity of Republican elected officials in Washington among the most ardent Republican voters.