If you lived somewhere where the GOP candidate is going to get 65 percent of the vote basically no matter what, and in the GOP primary you had an incumbent, somewhat average, right wing conservative that you've seen work across the aisle in the state legislator ruining against a hard core maga nut job, anti vaccine, anti public schools, openly racist etc. Do you think registering as a Republican to vote for the incumbent in that primary sounds like an okay idea? You can still vote for the Democrat and make your voice heard there at the general election even though it's essentially guaranteed he loses.
Or is the argument against this that if the crazy maga guy wins the primary there's a slightly better chance the Democrat can win? I'd call it unlikely where I'm at, but could see tighter districts working that way.