Why did Trump give up on electability concerns and shift from Cornyn to Paxton?

Maybe because after orchestrating defeats for Cassidy and Indiana state senators, he’s leaning into his “I’ll do whatever I want, whenever I want, for any reason I want” attitude, without regard for the consequences.
https://www.ms.now/rachel-maddow-show/maddowblog/trump-paxton-endorsement-cornyn-senate-talarico-democrats

Trump’s endorsement of Texas’ Paxton delights Democrats, frustrates Republicans

The Texas attorney general was understandably happy to get the president’s support. Oddly enough, Democrats were thrilled, too.

MS NOW
@stevebenen as the entitled rich child he is. + senile.
@stevebenen Corrupt, indicted, and a sex scandal. Paxton has the features needed for a Republican endorsement