In the early stages of the economic recovery a decade ago, most workers were primarily concerned with avoiding unemployment, said Celinda Lake, a Democratic pollster who has conducted research on voters’ economic concerns. But as the expansion has plodded on, the focus has shifted from having any job to having a good job, which workers see as rare.

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“You’re really trying to do something about what jobs pay,” Ms. Lake said.

With people increasingly open to more radical tools for accomplishing this, joining a union can seem downright middle of the road. According to recent polling by Pew Research Center, 42 percent of Americans view socialism favorably, up from 29 percent in 2010. During roughly that same time, support for unions has climbed significantly, from less than half to about two-thirds of Americans.

The increased openness to unions and collective bargaining has dovetailed with a palpable shift in expert opinion. For decades, economists tended to play down the importance of unions, attributing much of the increase in income inequality to a growing demand for skilled workers that resulted from automation and the spread of information technology. Some otherwise liberal economists were skeptical or even hostile to unions, seeing them as cartels that drove up wages for their members at the cost of reducing employment.

“I learned this in graduate school in macro — anti-union stuff from people who were highly inclined toward government redistribution,” said the economist and columnist Noah Smith, who earned his Ph.D. at the University of Michigan and has written about economists’ suspicion of unions. “There was this definite anti-union bias among liberals in the economics profession.”

But in recent years, many economists have begun to reconsider those views. Partly this reflects a broader ideological shift in the country away from the market-friendly policy approach of the 1980s and ’90s, which has lost credibility as inequality has widened. “We as social scientists live in a society where clearly the general social and political environment affects the questions we ask,” said Arindrajit Dube, a labor economist at the University of Massachusetts Amherst.

And partly this reflects a proliferation of research, which some of the campaigns have specifically cited, showing that employers have considerable power to hold down wages below the level the market would set.

Whatever the case, there appears to be a growing consensus among center-left economists that unions are a critical check on the tendency of capital to vacuum up the gains from economic growth. A recent paper by economists at Princeton and Columbia showed that unions raised wages for low-skilled workers in the decades in which inequality was narrowing and concluded that unions have “had a significant, equalizing effect on the income distribution.” A recent paper by the centrist Hamilton Project concluded that “unions lift wages, reduce inequality, and shape how work is organized.”