sort of.
in the
primaries you vote for a candidate from one of the parties to secure delegates at the convention. most states have "closed primaries" where only registered members of the party may vote for a candidate from that party. a few states have "open primaries" where people can vote for whichever candidate regardless of the voter's party affiliation. this election is interesting because it's hard to say who will have the nomination on either side, and there's a lot of "strategic" voting for both parties.
once the candidates are settled and the tickets are picked after the conventions, then they gear up for the general election in november when any registered voter can vote for any candidate/ticket. so independets/undecided/lazy people get thrown into the mix.
frankly, the system is bloated and stupid and costs way too much money. the campaign's been going on for over a year and very little governing has happened as a result. oh well, it's our * up brand of democracy.