“The Democratic Party pushed through the financial regulation of the 1930s, while the Democratic party of the 1990s undid much of this regulation in its embrace of unregulated financial capitalism,” the four authors write.

They cite the crucial role of congressional Democrats in enacting the Interstate Banking and Branching Efficiency Act of 1994, which eliminated past restrictions on interstate banking; the Gramm–Leach–Bliley Act of 1999, which repealed the 1933 Glass–Steagall Act separating commercial banking from other financial services; and the Commodity Futures Modernization Act of 2000, which restricted government oversight of most over-the-counter derivative contracts, including credit default swaps — all of which played a role in the financial crisis of 2007-2009.

The critique of the increased Democratic dependency on the rich by Bonica and his co-authors is modest in comparison to that of Martin Gilens and Benjamin Page, political scientists at Princeton and Northwestern. In a 2014 essay, “Testing Theories of American Politics: Elites, Interest Groups, and Average Citizens,” they analyze congressional voting patterns and conclude that

The majority does not rule — at least not in the causal sense of actually determining policy outcomes. When a majority of citizens disagrees with economic elites or with organized interests, they generally lose.

“These findings may be disappointing to those who look to the Democratic Party as the ally of the disadvantaged,” Gilens wrote in a 2012 essay published by the Boston Review:

In some respects Democrats have in fact served this function in the social welfare domain. But in other domains, policies adopted under Democratic control are no more consistent with the preferences of the less well off than are those adopted during periods dominated by the Republican Party.

Gilens, in a forthcoming paper in Perspectives on Politics, is critical of both Democrats and Republicans:

On important aspects of tax policy, trade policy, and government regulation, both political parties have embraced an agenda over the past few decades that coincides far more with the economically regressive, free trade, and deregulatory orientations of the affluent than with the preferences of the middle class.

Gilens notes that policies popular with the middle class but not with the affluent rarely win enactment:

The majority are redistributive policies including raising the minimum wage or indexing it to inflation, increasing income taxes on high earners or corporations, or cutting payroll taxes on lower income Americans.

Conversely, policies opposed by the middle-class but backed by the affluent include “tax cuts for upper-income individuals, spending cuts in Medicare, and roll-backs of federal retirement programs” – policies that have been adopted.

All these findings raise questions for those who would like to see the Democratic Party return to its more populist roots. Such a development faces two major obstacles.

The first is exemplified by the candidacy of Bernie Sanders, the Vermont independent-socialist senator seeking the Democratic presidential nomination.

Sanders is running on an explicitly left-populist platform. It includes taxation of overseas corporate profits, a progressive estate tax, an increase in the minimum wage to $15 an hour by 2020, the investment of $1 trillion in infrastructure, withdrawal from Nafta and other trade agreements, free tuition at public colleges, a single-payer health care system, and more.