The most inspiring campaigners, Senator Sanders on the left and Donald J. Trump on the right, did not convince voters of the wisdom of carefully honed policy prescriptions. They ran on an apocalyptic vision of America under siege, with clear enemies in sight. Mr. Trump, an interloper of scant ideological baggage who took over a Republican Party at least as clueless as Democrats about voters’ preoccupations, offered the more powerful apocalypse.

The question for Democrats looking for a path out of the wilderness — for Mr. Cowan and Senator Sanders; for Senator Warren and the Senate minority leader, Chuck Schumer, who hopes to woo voters by offering a “Better Deal” — is whether they can appeal to voters still angry because their lives, their aspirations and their sense of self have been derailed over the last few years.

The problem is hardly unique to American politics. Across the Atlantic, populist parties have arisen to rattle the established political class, though nowhere have they achieved the sort of upset pulled off by Mr. Trump.

Two years ago, three economists from the Free University of Berlin, the University of Bonn and the University of Munich published an analysis of the political fallout from financial crises in 20 advanced economies, including the United States, over the last 140 years. On average, they estimated, far-right parties increased their share of the vote by 30 percent in the years after the crisis, as voters blamed minorities and foreigners for their plight.

Voting for governments in power declined, and the share going to the opposition grew. Politics became more fractionalized as voters who lost faith in standard political pitches sought alternatives. Governing, of course, got much tougher. And some of these effects persisted 10 years or more.

It is hardly surprising that government — not Wall Street or big business — gets the blame. As noted in another study by economists at Princeton, the University of Chicago and the University of British Columbia, it is the government that mediates the competing interests of creditors and debtors.

Banks got a bailout after the financial crisis of 2008. Homeowners whose mortgages were underwater got next to nothing.