The Montana Republican Party filed a lawsuit last year, arguing that Montana’s open primary violates freedom of association for itself. Oral arguments are set for November 19, 2015. On October 23, the party filed its reply brief. That brief insists that if Montana requires parties to nominate by primary, then the state is obliged to set up registration by party on the voter registration forms.
The brief says, “The State’s refusal to register party affiliation severely burdens the ability of the Montana Republican Party to reach its members during the primary elections…by forcing the Party to participate in a state-run primary, the State removes the authority to select Party nominees from a small number of Party delegates to an electorate consisting of all of Montana’s 626,000 voters, all of whom are eligible to vote in its primary…the Party cannot identify its members amongst these 626,000 voters…Because the State’s mandatory open primary system severely burdens the Party’s constitutional right to identify its members, the State is obliged to ameliorate this burden by registering voters’ party affiliation.”
The party also says, “The State claims the Party ‘has apparently chosen not to create or maintain an official membership roll.’ This is false. The Party has attempted for decades to generate a list of its voters, but cannot create an accurate one.”
As far as is known, no party has ever asserted in a lawsuit that the U.S. Constitution requires a state to put a question about party membership on voter registration forms, if that state requires parties to nominate by primary. The claim that the party “cannot” create its own list of members seems unconvincing. Parties all over the world manage to build a membership list, without the help of government.