It seems insane to me to allow one party's voters to help determine who their guy gets to face in the final election. Why would any Republican want Democrats voting on who their candidate is, and likewise why would any Democrat want Republicans influencing their choice of candidate?
Most primaries are now "open." ANYONE can vote on ANY "side." This has been promoted as a "reform". At first, independents were given the ability to vote in ANY party (since before they had no voice in the primaries). But then ALL were given this ability. It's been promoted as "more democratic" and was seem as getting the Independents involved and was promoted as meaning less radical candidates would tend to become the nominees. I don't know if I agree with any of that, but that aside, it has been to a LOT of games. And it's largely destroyed the process, especially in states like California where the by far the Democratic party is the largest, followed by the independents, and with Republicans being a rather small minority: our primary is no longer ours. And hasn't been for some time.
When BOTH parties have very close primaries where a genuine choice is before the voters, people TEND to stay in their own party. BUT... when their own party's choice is wrapped up, people tend to vote on the other side - perhaps for who they think is the most acceptable candidate of the other party, sometimes for the one they think would be easiest to defeat. And in some states (like mine) where one party is MUCH larger than the other, even if a small percentage of Democrats choose to vote on the Republican side, it can sway the vote enough to change who wins - and that matters because this is a "winner takes all" states, the one who wins the primary gets ALL the delegates (no matter how close #2 was).
As the press has stressed, Trump is being helped by Democrats and Independents voting on the Republican side. This is usually all over by the time California votes, but often Democrats are a major influence on which Republican wins here. And there are more delegates in CA than any other state (by far).... and it's "winner-takes-all." IF Trump has not reaches the 1250 or so delegates needed by then, CA may well put him over the top. We'll see how this CRAZY election year pans out.
