An expert report commissioned by the state to defend its current primary election laws in a federal lawsuit includes this insight into party politics: Political parties in America have three "interrelated components," according to the state's experts, Andrew Martin of Washington University in St. Louis and Kyle Saunders of Colorado State University: The party in the electorate, the party in government, and the party organization. The party organization is the most ideologically extreme of the three; its goal is to promote the party label and positions and motivate its activists.

Party members who are elected to office tend to be less extreme; their goal is "to continue winning elections and therefore hold power." That requires moderate enough views to appeal to a general election constituency.

The party in the electorate - voters who identify with the party - are the least ideologically extreme of the three groups. Their goal is "to vote and have their voice heard."

Closed primaries lead to more-extreme candidates, the two professors wrote, with old-fashioned party "machine" politics the most-extreme example. "Open primaries produce less ideologically extreme candidates than closed primaries, and produce candidates that are more representative of the party in the electorate as well as the overall electorate," they wrote. "Open primaries increase citizen engagement as well as voter turnout in primary and general elections."