That's a really weird definition of "political party". I don't know of any country that has political parties by that definition.

I'm not aware of any law that requires primary elections. As I understand it, that is a decision by the two major parties.

But I don't think it would help this cause either way. The author wants a party to be able to enforce ideological purity. That's going to pare your party smaller and smaller, until it's a party of one.

If ideological purity is your goal, then you can just write yourself in to every election. And then you will spend a few years under the governance of somebody who was able to make compromises and get a plurality of votes.

I don't think the law is this guy's problem. But even if it were, he'd immediately run into a million other problems.

> One solution regularly proposed is that the left needs to break with the Democrats and build a third party

Disenfranchised Republicans have spoken this out loud too, but third parties fail in the US because of money. It takes a lot of money to organize enough people to get on all ballots in all jurisdictions. Most Americans otherwise lack sufficient interest to help achieve this.

The other side of the problem is attempts to superficially game the system through artificial candidate selection via primaries and first past the poll voting mechanisms. Once you eliminate those politics does a 180 converting from toxic to exceptionally pleasant.

YES THEY ARE ILLEGAL BECAUSE THEY ARE RUINING THE COUNTRY.