An OUR Walmart protest from 2012, the early days of the campaign. (Photo by flickr user Neon Tommy under a Creative Commons attribution license)

On Wednesday, thousands of low-wage workers walked off their jobs in a nationwide action pushing for something that once seemed outlandish: a $15 minimum wage. The demand has gone from pie-in-the-sky to almost mainstream in the span of a couple years, as workers across the country have made the case that nothing less than that is enough to live on, and major corporations like Wal-Mart and McDonald's have started to budge.

There’s another piece to the sloganeering in the streets, though. Once in a while, you’ll see a sign that says “$15 and a union.” And, indeed, though many religious and community groups have supported the Fight for $15, it’s fair to say it would never have gotten this far -- spreading from fast-food workers to adjunct professors, home health aides, child-care workers and more -- without the financial and logistical support of Big Labor.

But there’s a looming question behind that helping hand: What if it never turns protesters into dues-paying members? Actually winning elections at giant employers like Wal-Mart and McDonald's, which have gone to great lengths to deter unionization, appears nearly impossible. What if the unions’ return on that organizing investment, besides the satisfaction of having helped workers more broadly, is essentially zero?

[Read more: Protests for $15-an-hour wages are picking up more allies]

Over the years, there’s been some tension within the unions about how much to spend on an effort that isn’t a traditional organizing campaign and doesn’t focus on unionized employers. This month, the New York Times referred to “grumbling” within the Service Employees International Union, which has bankrolled the Fight for $15 campaign to the tune of $15 million.

Protesters seeking higher wages for fast-food workers marched on the streets of New York Wednesday. (Reuters)

And now, according to multiple sources close to the United Food and Commercial Workers’ OUR Walmart and Making Change at Walmart campaigns, which have helped workers wage strikes and protests since 2011, the union has slashed campaign funding by more than 50 percent since new leadership was elected in December.

"The new president campaigned internally hard against the campaign and the resources spent on it,” said one person, who spoke on the condition of anonymity because she was not authorized to speak to the press. “It's a shame not to capitalize on the first real major victory by driving harder at them, a real wasted opportunity for those workers."

Unlike the SEIU, the UFCW doesn’t break out the amount it’s spent on the Wal-Mart effort in its public disclosures. It has supported various organizing efforts at the world’s biggest retailer for decades, and 10 years ago it shifted to a public strategy rather than going store by store. But in 2013, it pledged to stop trying to unionize at Wal-Mart stores after the company accused it of illegally picketing; all OUR Walmart efforts are now purely aimed at bettering wages and working conditions for employees.

The most recent IRS filings for OUR Walmart show that the organization took in $239,000 in 2013, but that was mostly for used hardship payments to workers who lost wages due to going on strike or getting fired. It doesn’t include the salaries of dozens of full-time organizers who at one time were assigned to the campaign -- many of whom are now being reassigned to other priorities -- or cash assistance to groups like Jobs with Justice, which have also worked to build support.

Although declining to comment specifically on funding levels, the UFCW denies that it’s drawing down the Wal-Mart campaign.

“The UFCW has been relentless in our fight to raise standards at Walmart and has been at it for more than 30 years of activism and campaigning,” communications director Jill Cashen wrote in an e-mail. “We will not stop until the hardworking men and women at Walmart have the better life they deserve.”

Indeed, said another person close to the campaign who spoke on the condition of anonymity because he was not authorized to speak publicly, OUR Walmart will maintain its largely Facebook-based organizing work. "The campaign’s online program relies largely upon Wal-Mart workers taking leadership and organizing their own co-workers, even where there isn't an organizer on the ground,” the person said. “My understanding is that they will continue to build upon that model." The AFL-CIO has also supported OUR Walmart financially, and a spokeswoman said it will continue to do so.

The UFCW’s shift illustrates the challenge of justifying investments in campaigns that primarily benefit non-members, when union workers expect to see their dues go toward better contracts that improve their wages and benefits. But there’s a practical rationale for trying to raise Wal-Mart’s wages: It can help provide leverage in those contract negotiations. Unionized employers like Kroger, Giant Foods and Safeway frequently argue that they have to match wages at competitors, so raising the market wage enables the union to win more at the bargaining table for members.

Still, only really robust unions have resources left over to fight that outside battle. UFCW’s membership has been slowly declining. The SEIU’s membership, on the other hand, swelled during the 2000s before flattening out. That makes it easier to afford initiatives like the Fight for $15. And it also reflects a belief that the “union premium,” or the difference between what union and non-union members make, is something that should decline, not increase.

“A high union premium is a sign of weak, not strong unions,” says Mark Levinson, the SEIU’s chief economist. “When unions are strong they set the wage norms that prevail throughout society. Strong unions also use their political power to enact public policies that raise the floor for all workers.”

In large part, that’s what’s been missing over the past few decades of stagnant wages. SEIU is gambling that it can turn that trend around, whether it means more members or not.

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