WASHINGTON -- President Barack Obama has made it clear that income inequality will be his defining issue in 2014. If such a strategy helps him advance his policy goals -- and if it pays out dividends to his fellow Democrats in the midterm elections -- then the president and his party will have a lot of low-wage workers to thank for their boldness.

Months before David Brooks and Paul Krugman were dueling over inequality in The New York Times op-ed pages, thousands of low-paid workers were walking off their jobs in fast food and retail to protest poverty wages . The workers may have had the strategic backing of labor unions, but they had no formal representation in the workplace and no contracts. At close to minimum wage and no benefits, many of them simply felt they had nothing to lose.

Without footage of those mass walkouts hitting the news, it isn't so obvious that Washington's elite would now be talking in earnest about the growing gap between the McDonald's executive, who makes $8.75 million a year , and the McDonald's cashier, who makes $8.25 an hour. The discussion itself -- expected to be the focus of Obama's State of the Union address next week -- may be something of a victory for a labor movement that's spent much of the last few years on the ropes.

"Working people have been stepped on so hard that the rise of a national conversation on falling wages is not entirely a surprise to us," said Damon Silvers, policy director at the AFL-CIO labor federation. "But it matters what, and who, is driving the conversation. The fact that workers at Walmart and in fast food are striking outside of the historic collective bargaining structure is a really powerful thing."

Striking low-wage workers have put a face on one of the president's top policy objectives -- raising the minimum wage and pegging it to inflation. The president initially proposed a hike to $9 an hour last February, but he's since gotten on board with congressional Democrats' more ambitious bid of $10.10. That alone is proof that workers have already altered the debate, according to Mary Kay Henry, president of the Service Employees International Union, which has coordinated the fast-food strikes.

"The workers showed courage, and he moved to $10.10. It's already having an impact," she said.

What remains to be seen is whether the White House will continue to pour significant political capital into raising the wage floor, or instead into something like a fast-track of the Trans-Pacific Partnership trade deal, which has heavy opposition from unions and progressives. Despite their 2012 alliance, the relationship between Obama and organized labor is an uneasy one. As encouraged as they are by Obama's focus on income inequality, labor groups are waiting to see how he turns that talk into policy.

For the wider labor movement, the timing feels ripe for a large-scale policy victory. The slowly improving economy is returning some bargaining power to workers, while the high-profile strikes of 2013 have served as a shot in the arm after devastating state-level setbacks in places like Michigan and Wisconsin. And with union density having fallen to historic lows, the AFL-CIO is refashioning itself to welcome into the labor movement other progressive groups and non-union workers, much like the Taco Bell and Walmart workers who've taken to the streets.

"I think the broader labor movement needs to realize -- certainly coming off the AFL-CIO convention this year -- that they need to be in the business of advocating for the full working class and the poor, not just existing members," said Sarita Gupta, executive director of Jobs with Justice, a national workers' rights group. "It's about a broader population of people who need us to be advocating for better wages and working conditions, and turning the tide on spiraling downward trends."

While the hard numbers may be dispiriting for labor -- just 6.6 percent of private-sector workers now belong to a union -- there are encouraging signs on the state and local levels. The election of Bill de Blasio in November showed that a progressive pro-labor candidate could still become mayor of New York City. Meanwhile, the same election season brought labor-backed minimum wage raises to New Jersey and, in grander fashion, to SeaTac, Wash., where voters approved a measure establishing a wage floor of $15 at certain businesses -- the very demand made by fast-food workers.

The victories have been just as widespread with another priority of the labor movement, one that's emblematic of new progressive alliances: paid sick leave. Disproportionately, it's low-income workers who don't have the basic benefit of paid time off from work when they're ill. In the past couple of years, partnerships between community, faith and labor groups have helped push through sick-leave mandates in various cities around the country, and now they're brewing at the state level. They've been so popular that business lobbies are now trying to block the measures before they can even get on a ballot.

These local efforts on the minimum wage and paid sick leave have come in lieu of action by lawmakers in Washington, as the GOP-controlled House has no appetite for putting such mandates on businesses. But the legislation that's happening on the local and state levels is having an immediate impact on working conditions, said SEIU's Henry.

"We have to stop imagining a policy fix at the national level and start supporting workers," she said. "What we're seeing in the low-wage service sector is workers coming together and saying, 'I'm worth more.' If we stand with them, they're going to create the next path."

Even with gridlock on the Hill, there are steps that Obama can take on behalf of low-wage workers. Just in September, the White House announced a new federal rule extending minimum wage and overtime protections to 2 million home-care workers, many of whom work long hours for low pay and have been traditionally carved out of labor law. Although there were objections from the industry and from Republicans , the rule does not require an act of Congress.

Rep. Keith Ellison (D-Minn.), a chair of the Congressional Progressive Caucus, said he hopes to see more actions like that from the president. In particular, Ellison has been urging Obama to issue an executive order setting a living wage for low-wage workers under federal contracts, some of whom have also gone out on union-backed strikes in recent months. It would be one way to raise the minimum wage for thousands of workers, even if Democrats can't manage to pass their own minimum wage bill.

"There is precedence for this," Ellison said. "No matter what he does, Republicans are going to complain. That shouldn't be anything to stop him."

Progressive members of both the House and Senate have called on Obama privately to issue the executive order, although the White House has remained mum on the idea in public. Such a bold, unilateral move would surely rankle Republicans and a few powerful business lobbies. But it would also send a strong message that the president plans to tackle income inequality beyond his speeches, and that he'll do so with or without the cooperation of Congress.

This article is part of a weeklong series examining income inequality in America in advance of President Obama's State of the Union address. Read more here .