The Primary Elections are not required by any Federal Law, and essentially have no real legal standing. They are generally "authorized" by the State Legislatures, where the State contributes anything to running them, or where State laws require "oversight" by State Election officials (to assure honesty;<(); but are essentially for the sole benefit of the Parties.

The pretense is that they are to give the Party Members in a given state the opportunity to choose which candidate(s) they want to have representing them in the General Election.

In nearly all states you must generally register in advance of the General Election. Some states, historically, allowed you to vote if you could show "credentials" at the polling place, without registering in advance; but I don't know of any where that's still common. Some states will allow you to cast a "provisional ballot" if you're unregistered at the time of the General Election; but in most places that accept provisional ballots they're only counted in case of a tie, or if the vote is "contested," and then only if those doing the recount "get around to them."

In most of the states that have primaries, the Party determines who can receive a ballot, although some states require "approval" of the Parties' rules by an Election Commissioner or other State official. And in most cases it's the general rule that you must be Registered as a "party member" in order to get a ballot.

That "general rule" is modified in some places by your right to declare, or change, your party affiliation at any time, and in some states you are legally permitted to say "I used to be a #@$!% but now I'm a %!$@#$ at an election and get a ballot.

Due to the hazy legality of the Primaries, the states do vary in whether they consider your Primary vote to be a "public record" or a "secret ballot." Due to the frequency of "contested votes" it is necessary for someone to be able to know what person cast each ballot, and what choices were shown on that ballot, in order to know which ballots to count and which to disallow. Since "someone" is nearly always a "committee" or at least a group of delegates assigned to verifying the ballots, the maxim quoted in another thread here recently should be remembered:

"Three people can keep a secret - if two of them are dead."

(While the above maxim is attributed to "a Mafia Don" it probably is well known to politicians.)

The closest anyone can come to a "general rule" on primaries is that Republicans vote in the Republican Primary and Democrats vote in the Democrat(ic) Primary. While there are attempts to maintain that your ballot is "secret," your party affiliation generally is a public record, and the requirement that you declare an affilication in order to vote in a primary means that you cannot conceal your "affiliation" with the party and will receive appeals for donations - probably for the rest of your life regardless of any changes in your subsequent declarations of affiliation.

In Kansas, a couple of elections ago, it was published that there were 19 registered Communists, similar numbers registered with three or four other "fringe" parties whose names nobody can recall - and numbers of registered Democrats and Republicans in each precinct were given - in most local newspapers and on TV News(?) reports.

The worst thing about being registered probably is the campaign appeals, and the constant "newsletters" from candidates (now often via email).

I'm sure it's all clear now.

(?)

John