Ballot Access News:
"The bill will also make it possible for voters to register as members of unqualified parties, and election administrators would recognize those registrations and keep a tally. Currently, the New Hampshire voter registration form has a blank line in the question about political party choice. But even though any voter can write in the name of an unqualified party, elections officials treat such voters as independents.
New Hampshire is the only New England state in which only the Democratic and Republican Parties are ballot-qualified. "