In the movie Crimson Tide, nuclear submarine Capt. Frank Ramsey (Gene Hackman) schools Lt. Cmdr. Ron Hunter (Denzel Washington) on questioning the orders of superiors. He says, "We're here to preserve democracy, not practice it." You can say the same about the traditional roles of the main political parties in the United States, where those who know all the ins and outs, rules, data points, and political terrain have long shaped internal elections behind the scenes. Party leaders' No. 1 task was to filter out bad candidates and recruit and promote the good ones. Parties were a vehicle for what was in the best interest of the parties, which purported to represent their members. This, of course, can be used to nonmembers' advantage. Libertarians and socialists, for example, align with the GOP or Democratic Party...