On January 10, the Montana Republican State Central Committee voted 83-43 to add the state party’s name to the list of co-plaintiffs, in Ravalli County Republican Central Committee v McCulloch, 6:14cv-58. See this story. The lawsuit, filed by some county units of the Montana Republican Party, says that the party has a constitutional right to prevent members of other parties from voting in its primaries, especially for party office.
Montana has open primaries, which means that on primary day, any voter is free to choose any party’s primary ballot. If the lawsuit wins, the state legislature will probably alter the voter registration form, to ask applicants to choose a party or independent status.
Montana only has three qualified parties: Republican, Democratic, and Libertarian. The Democratic and Libertarian Parties will be free to continue letting any voter vote in their primaries, if the Republican Party wins the lawsuit. Generally, though, the Montana Libertarian Party doesn’t actually have a primary, because generally no more than one candidate files in the Libertarian primary for any particular office. When that happens, election officials don’t print up primary ballots for the Libertarian Party.