My best guess is Trump is watching how Talarico polls out the gate before picking between Paxton and Cornyn....
If his whacky blaspheme past persists and impacts his polling, i.e. showing the seat is safe, i am guessing the nod goes Paxton. Let's not forget that Paxton was on the AG short list late last year. Trump rewards loyalty.
If it is close, RNC, and Wyles will advise him to stick with Cornyn.