Fast-food workers in more than 150 cities staged another in a series of one-day strikes on Thursday. At least 19 people were arrested outside of a New York City McDonald’s. The workers’ “Fight for 15” campaign, an effort to win $15 hourly wages and contracts from some of the nation’s largest employers, most particularly McDonald’s, has been building steadily since a small band of employees first walked off the job two years ago in New York.

By the conventional metrics of organizing projects, the workers’ effort, backed and coordinated by the Service Employees International Union, is a work in progress at best, a quixotic venture at worst. The great unionization campaigns of the 1930s and ’40s focused on factories that employed thousands. McDonald’s offers unions no such economies of scale: The hundreds of thousands of people who work for the company and its franchises are scattered among thousands of small outlets. It’s hard to see how even a rising number of sporadic strikes by discrete groups of employees will bring McDonald’s to the bargaining table anytime soon.

Still, even though the campaign has yet to win a union contract for a single worker, it already has to be judged a signal success. By highlighting the abysmal incomes of millions of hardworking Americans, it has prodded governments to phase in minimum-wage increases in a growing number of cities and states. California has raised its minimum to $10; Massachusetts, to $11; the District of Columbia and its Maryland suburbs to $11.50. Seattle has hiked its minimum to $15, and San Francisco voters are expected to do the same at the polls in November. San Diego recently raised its standard to $11.50, and on Monday, Los Angeles Mayor Eric Garcetti proposed raising his city’s minimum to $13.25 — roughly the same level that New York Mayor Bill de Blasio and Chicago Mayor Rahm Emanuel are pushing for. Other legislation targeted at low-wage workers is being enacted, as well: Last week, the California legislature, with the backing of Gov. Jerry Brown, passed a bill mandating paid sick days for the state’s workers.

The fast-food workers’ campaign, then, may be viewed not simply as a unionization drive but also as the second act of a broader workers’ movement kicked off by the Occupy Wall Street demonstrations of 2011. Occupy never developed a strategic focus that went beyond occupying, but it nonetheless focused the nation’s attention on the widening chasm separating the 1 percent from everybody else. The fast-food campaign, similarly, has not produced — not yet, at least — anything resembling a union contract, but it has staged enough high-profile actions, with a compelling economic and moral message, to win real gains for workers, whether those workers stand to ever become union members or not.

The unions’ victory in Seattle — together with its small, suburban adjunct, SeaTac, the only cities to have gone all the way to $15 — is emblematic of the way workers win today. Initially, unions hoped simply to win contracts for the 6,000 service-sector workers at Seattle’s airport and the surrounding hotels. When employers resisted, the unions threatened to place a $15 wage proposal on the SeaTac ballot (the airport is located in SeaTac), but still the employers wouldn’t negotiate.

To everyone but the unions’ surprise, voters approved the measure last November. In Seattle proper, SEIU leader David Rolf timed fast-food demonstrations to coincide with major events in that city’s mayoral election, even succeeding in getting eight of the nine candidates to a televised debate in which all the questioners were low-wage workers. The eventual winner, Ed Murray, took the strongest stance in favor of the $15 standard, and, emboldened by the victory at SeaTac, steered a business-labor negotiating team and then the city council to enact the $15 ordinance this summer.

Instead of unionizing 6,000 workers, then, the unions engineered a major raise for an estimated 100,000. In today’s America, workers can still mobilize and win, but their victories are far more likely to come in the political and legislative arenas, where unions retain some power, than in actually building unions, which the weakness of U.S. labor law renders nearly impossible. The challenge before unions, then, is how to maintain and devise organizations that enable workers to have bargaining power — at the ballot box, in the halls of government and, perhaps, ultimately, in the workplace again — when employers and the law are arrayed against them, and when the workers they champion aren’t dues-paying members who provide the funding for their endeavors. Absent such organizations, workers’ ability to bargain — at the polls no less than on the job — will eventually disappear.

Harold Meyerson is editor-at-large of The American Prospect.