Expel them, if possible. The nature of a party requires SOME modicum of party discipline. You can’t just call yourself “Republican” because, well, you SAY you are one — at least not in public office. Insane.
Imagine if a group of Democrats endorsed a Republican for re-election of a Democrat. The REST of the Dem party would be outraged, and they should be.
“Imagine if a group of Democrats endorsed a Republican for re-election of a Democrat.”
This does not happen anywhere, ever. The democrat party has iron discipline when it comes to control over their members. I used the term “iron discipline” deliberately; it’s Lenin’s legacy.