Easy when it's an open primary of course - anyone can vote - could be done in a much looser effort. Harder in a closed state - some states control how often you can switch parties. Much more difficult to coordinate a massive party switch in a closed state. Obviously much easier to control a party-switching problem in a closed state.
Open primaries make no sense to me and as far as I'm concerned it is a fiasco for the party holding the primary.
The Virginia GOP is requiring voters to sign a loyalty oath to vote on the GOP ballot March 6th. That’s probably as close to a closed GOP primary we will get in Virginia. No doubt, a closed primary would give the party more control. I’m not aware of any movement to include party affiliation on the voter registration database.