What's the purpose of a primary election? It's to select a party's candidate for a general election. It's not very obvious that this should even be a democratic process, but if it is, why shouldn't party members be the ones selecting their own candidates?

How do you envision this working without the "opposing party" poisoning the vote to get a weaker opponent?

Is actual party membership required?

Or, in effect, are you just required to claim either that you're more of a cat person, or that you're more of a dog person?