Voters may or may not choose to affiliate with a political party, however, affiliation with a party is required to vote in primary elections.
42%of New Hampshire voters are registered as undeclared.
Details of voting in congressional and state primary elections:
Voters must affiliate with a party to participate in that party's primary.
An unaffiliated voter may choose one party's ballot, which makes them a registered member of that party. However, temporary affiliation is possible, as voters can fill out a card at the polling place to return to undeclared status after the vote is cast. For this reason, New Hampshire allows same day registration for unaffiliated voters