Castro is a face palm in TEXAS. Even one fed up donor is dropping him on his head. Castro has made an azz of himself on every occasion and even the Dems have taken notice.
Warren would never pick Castro. She, herself, is enough to carry the radical Mexican vote, so she does not really even need Castro to step any further into the radical lane just to show how much more communist he is than she. It would cost her in the same states Trump took that were so key to the electoral vote.
Heck, she conceivably pick Bernie just to Unify the Party and serve that Labor vote in those key states.
How about Manchin?
I know he is angling for that.