The question is whether he legitimately changed his view on the issue. But I’m still not sure what you meant by his being a “spoiler.”
If he takes the primary, he’ll lose the general and have spoiled the chance Republicans have of taking Hooley’s seat.
Mannix is a perennial political whore whose only real interest is securing a sinecure for himself so he can continue to suck from the public teat while milking the lobbyists.