The first is a populism of substance. It is motivated by justified outrage at specific instances of injustice and corruption in the economy and political system, as well as a generalized sense that the political and economic order of the United States has evolved to serve the interests of the few at the expense of the many. It looks with disgust on the self-dealing and influence-peddling that infects both Wall Street and Washington, leading elites in both places to grow filthy rich while the rest of the country sees its jobs vanish and wages stagnate over time. This form of populism hopes for policies that address these problems, including structural reforms to keep big government, big business, and big banking from colluding in ways that clash with the interests of ordinary Americans.

Democrats and Republicans both fear and long to tap into this populist energy — but ideological commitments as well as concerns about holding together long-established electoral coalitions keep either party from embracing it wholeheartedly or consistently.

On the Democratic side, Sen. Elizabeth Warren (D-Mass.), for one, favors slapping the banking and corporate sectors with stronger regulations, but she has much less interest in reining in the size, power, and scope of government.