My partner is angry that I spent several years after Bernie lost shitting on prison abolition for no discernible reason (pleasing the whites). They seem to be angry now that Kamala is the nominee and I'm suddenly a huge supporter of calling her a cop - am I the asshole? (no)
Being for US prison abolition is a good position and so is opposing Kamala, for a number of reasons that include her "top cop" prosecutor past.
Whether you're "the asshole" isn't really about having exactly the correct political positions, though, it is mostly whether you are treating your partner well. For infosec reasons I won't ask for that info in any detail, but I would suggest asking yourself whether you have approached your partner about this in a way thatbis respectful to them, acknowledges that your own positions have shifted over time, and includes offering to explain why you feel the way do?