The concept of self-excommunication for supporting pro-choice candidates is a doctrine of the Church.
True - but the Catholic Church doesn't recognize it's own (self-)excommunications as valid when it comes time to count membership. How else could there be 68+ million Catholics living in the United States right now?
As Wuli said in post 13, "somebody didn't get the memo".
This is sticky. Is excommunication simply a mortal sin that can be forgiven in the confessional? I don’t think so. What makes him excommunicant rather than simply unable to receive communion is the public acknowledgment of his public disobedience—which may or may not follow. If he lives in the Diocese of Santa Fe, it may well follow. If he doesn’t, who knows?