Fast-food workers and their allies in the “Fight for 15” movement who were gathered Sunday in Detroit to plan strategy for action in the streets and at the ballot box got an unexpected call from the frontrunner for the Democratic presidential nomination and, perhaps, the presidency.

Declaring, “I want to be your champion,” Hillary Clinton told the activists, “We need you out there fighting against those who would strip away Americans’ right to organize, to collectively bargain, to fair play. No man or woman who works hard to feed American families should have to be on food stamps to feed their own family.”

The Sunday morning phone call by the former secretary of state to the national gathering in Detroit was a breakthrough moment for the movement to raise pay for fast-food and retail workers, as it signaled that their issues are going to be a major part of the 2016 debate. It was also something of a breakthrough moment for Clinton, who has been seeking since announcing her candidacy to distinguish herself as a more progressive and populist contender.

But how much of a breakthrough remains to be seen. Clinton did not talk numbers in her call. Indeed, as CNN noted, ” Just how high a wage hike Clinton supports, however, remains a mystery. The candidate has not provided a figure yet. Her campaign did not return a request for comment Sunday night.”

Specifics are going to matter.

Facing a spirited economic-populist challenge from Vermont Senator Bernie Sanders, who has long championed wage hikes, and prodded by former Maryland governor Martin O’Malley, who has a track record of work on living-wage issues, Clinton could not avoid the debate about hiking wages; she had to offer the party’s base voters some economic populism. A recent Politico headline sums the circumstance up. “Hillary Clinton Camp Fears Bernie Sanders,” read one, while another declared, “Wall Street Fears Leftward Swerve By Clinton.”

To Clinton’s credit, her referencing of the Fight for 15 movement was not a mild reference. It was laudatory. “I hope that every one of you will continue to raise your voices until we get all working Americans a better deal,” the candidate told the fast-food workers who had come to Detroit from across the country. “I want to be your champion. I want to fight with you every day. I’m well aware that the folks on top already have plenty of friends in Washington, but we together will change the direction of this great country.”

Yet Clinton has not, as have Sanders and O’Malley, announced support for a $15-an-hour wage. And as with her relatively strong statements on trade policy—strong on principles, weak on precises stances—the specifics are what will matter.

Clinton is a savvy politician. She recognizes that the “Fight for 15” movement has traction—and that major labor unions and grassroots activists are starting to measure candidates according to their commitment to the fight. She has made a good statement, and gotten some good headlines. Now she must provide a sense of where exactly she stands on a federal $15-an-hour wage, on state and local fights, and on a host of other wage and work concerns. And, frankly, she needs to fill-in-the-blanks on related issues, such as the fight for a Retail Workers Bill of Rights and efforts to make it easily to organize and maintain unions.

Clinton’s formal launch of her candidacy this coming Saturday at the Franklin D. Roosevelt Four Freedoms Park in New York City will be a key test. Will she reference the Fight for 15 movement? Will she make this struggle a clear, and constant focus of her campaign?

The pressure will only increase for Clinton and the other 2016 candidates. Following the lead of Seattle, San Francisco, Los Angeles, and other cities across the country have moved to implement $15 wage floors, and states such as New York are starting to explore the prospect.

New York Governor Andrew Cuomo, who announced last month that he will convene a special wage board to review and recommend higher wage rates for fast-food workers, explains why this is the case. “Nowhere is the income gap more extreme and obnoxious than in the fast-food industry,” wrote Cuomo in a New York Times opinion piece. “Fast-food C.E.O.s are among the highest-paid corporate executives. The average fast-food C.E.O. made $23.8 million in 2013, more than quadruple the average from 2000 (adjusting for inflation). Meanwhile, entry-level food-service workers in New York State earn, on average, $16,920 per year, which at a 40-hour week amounts to $8.50 an hour. Nationally, wages for fast-food workers have increased 0.3 percent since 2000 (again, adjusting for inflation).”

As Service Employees International Union President Mary Kay Henry says, ” Powerful people around the world are listening to this movement to change our world.”

This is the context in which Clinton’s statement comes. Fast-food workers are organizing, and they are winning. Retail workers are organizing, and they are winning. Home-care workers are organizing. A movement has taken shape. It is real. And it has specific “asks” of candidates.

“We’ve got unstoppable momentum,” said LeTonya Wilson, 41, a Richmond, Virginia, McDonald’s worker who is paid $8.25 an hour. “Fifteen dollars is sweeping the country and we’re going to build off victories in places like Los Angeles, New York and St. Louis to win $15 in Richmond and all across the country. Everyone said we had no chance, but we’ve shown when we stick together and speak out, we get life-changing results.”

Wage hikes are life-changing for workers who are struggling to get by.

And the movement for wage hikes is changing American politics.

Presidential candidates are taking notice.

Indeed, the front-runner in the race for the White House is saying to LeTonya Wilson and her fellow workers: “There’s a lot we can do together and you’re showing us what that route is. You’re on the streets, your voices are being heard. We need you.”

That’s right. But that’s not enough. Getting a presidential front-runner to “call in” is not an indication that a corner has been turned on the “Fight for $15.” Rather, it is a signal that the 2016 contest could, with continued pressure on all the candidates—Democrats and Republicans and third-party contenders,; liberals and centrists and conservatives—be the moment when that turn is made.