Most Sunday mornings last summer, Julia Gould set up a table at the Hollywood Farmers Market. Alongside stalls selling shiitake mushrooms, free-range poultry and orange-blossom honey, she was selling an idea: a $15.37-an-hour minimum wage for the city’s hotel workers — more than twice the federal minimum wage and one of the highest minimum wages in the nation.

As shoppers wandered past, Ms. Gould asked them to sign a petition calling on the Los Angeles City Council to approve the proposal. She also urged them to write on a whiteboard their reasons for supporting the higher wage. One shopper wrote that “to live a healthy life, you need a living wage,” while a woman carrying a Starbucks coffee scribbled that she supported the idea “because rent is expensive.”

A second community organizer photographed these shoppers and their hand-scrawled signs and then posted those pictures on Facebook and Twitter, steering them to Mitch O’Farrell, the City Council member who represents Hollywood. Mr. O’Farrell had questioned the wisdom of the $15.37 wage proposal, fearing that it would force hotels to lay off some of the city’s 17,000 hotel workers. “We were trying to show him that his constituents cared about this,” Ms. Gould said.

Her politicking was one small part of a campaign orchestrated by one of the nation’s leading advocacy groups for low-wage workers: the Los Angeles Alliance for a New Economy, or Laane. Harold Meyerson, a Los Angeles native and syndicated columnist, has called the alliance “the nation’s most innovative and effective force for raising the incomes of low-wage private sector workers.” Laane estimates that its efforts have improved wages or benefits for 121,000 workers and yielded them $2 billion in economic benefits.