(Image: Shutterstock) T he 2016 election has thrust populist candidates and big-spending outside groups to center stage. These trends further marginalize the traditional role of the national political parties. Thrown on defense by angry voters, self-financed candidates, and billionaire donors who thumb their noses at the political establishment, party leaders are struggling to reclaim power. A growing chorus of political analysts, election lawyers, and even some progressives argue that the solution is to give parties the same freedom to raise unrestricted, high-dollar contributions that super PACs and other outside groups now enjoy. That, presumably, would partly restore the influence of parties, and serve as a more democratic counterweight to freelance mega-money. On paper, the notion that parties should operate by the same rules as freewheeling non-party players has appeal. Parties fully disclose their activities, are accountable to and committed to turning out voters, and act as a...