But constitutionalism limits the wants that are permissible. It does so by stripping party members of control of the selection of their candidates and hence of their message. In a blanket primary, a party's nomination can be won by a candidate other than the one who gets a majority of the party members' votes. The court has said states can require parties to select candidates by primaries but do not have carte blanche to dictate the nature of the primaries. In 1986 the court overturned Connecticut's law requiring closed primaries, siding with Connecticut's Republican Party, which wanted an open primary as a means of broadening its base.
Proponents say that by multiplying choices, blanket primaries increase voter participation.
There is much more to representation than elementary arithmetic. Parties are indispensable instruments of representation because they aggregate interests and articulate distinctive doctrines of justice. But parties cannot do this if they can be hijacked by drive-by voters with no durable interest in the parties, acting on transitory whims, or even to make mischief by burdening a party with a weak candidate. The court might flinch from ruling against blanket primaries because such a decision would have serious implications for the 23 states that have open primaries. It should not flinch.