Can political parties expel “members”? [duplicate]
What exactly is the status of a "member" of a political party in the United States? As far as I can tell there is no formal organization of political parties such as the "Democratic Party" and "Republican Party". People can apparently simply "identify" as a Democrat or Republican without actually having to apply to or be accepted by the party. In the old days political parties had membership cards but that is apparently no longer true.
As an example of the ambiguous nature of party "membership" the personage Elizabeth Cheney has apparently incurred the wrath of the Republican party, but there appears there is little they can do about it, other than direct their funds to some other "member" of the party. So a person can be a "member" of a political party in the United States, even though the party itself might not want that person to be a member.
We can imagine a situation where a disreputable person, let's say a convicted serial killer, describes themself as being a "member of the Democratic Party" and there is no recourse for the party to deny this? Or is there?
What exactly is the legal nature of a political party in the United States?
As a background I would point out that normally, it is a legal fact that any company or organization has a fundamental right to define who is or who is not a a member of that organization. However, this basic principle does not seem to apply to political parties in the United States. So, in that case, what principles do apply?