To me as a Canadian, the absurd part is that ordinary people are expected to have "registered" with a party (as opposed to registering with the independent organization that runs elections, like we do; they automate getting most of the voter roll from Revenue Canada, but this requires your explicit consent on the tax form).
I've never once registered with a party in the US. I always check "independent" on my voter registration. But I'm in a state with open primaries, so I can still vote in one or the other primary, even though I'm not registered with the party.
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?
I envision that it does not matter, because this is a tactic that would 1) be available to all, and 2) it gives up your vote for someone of your own party, thereby weakening your own position. It's self regulating.
Can't they do that now? If I think my chosen primary guy is winning in a landslide I could just register for another party I don't like and vote for someone who I think is easier to beat.
You would still forfeit the ability to vote in your primary though. I do think there are people that do this, but most people want to vote in their primary regardless of whether it's a landslide.
Yeah it's the latter. The US does not have party membership the way that, say, the UK does. In many states, it's open primary. In Colorado, for instance, I get mailed Democratic and Republican primary ballots and can vote by mailing in either one. I think you get neither counted if you mail in both, but I have no idea; I've never tried it.
The last time anyone tried to poison a presidential election by promoting a weaker candidate on the other side in the US, it was the Democrats boosting Trump in 2016. It did not work out.
For an alternate example, in Illinois you choose one at primary election time and only get that one. This year the options are Democrat, Republican, Libertarian, and Non-Partisan (which means only the referendums, not the elections).
This would kind of be the same as us (I'm Canadian too) registering with the NDP so we can vote for the next leader. But the level of lying on display here is just insane.