Vermont Senator Bernie Sanders says America needs a “political revolution” to change the debate about economic inequality and he sees evidence of the upheaval in Chicago. So the senator is wading into that city’s mayoral race as a backer of Jesus “Chuy” Garcia, the labor-backed progressive who is mounting a spirited challenge to incumbent Rahm Emanuel.

Sanders, an independent who caucuses with Senate Democrats, has been exploring a possible 2016 presidential candidacy as a progressive-populist challenger to the Democratic establishment. And he argues that Garcia is forging the sort of “working-class coalition” that is needed to shake up politics in urban America and beyond.

Garcia earned headlines with a strong showing in Chicago’s first round of voting in February. That forced Emanuel into a rare runoff for mayor of the nation’s third largest city. Emanuel, a politically-connected Democrat with close ties to Wall Street and corporate interests, still has a big money advantage in the race (with many donations from wealthy Republicans)—and a lead in most polls. But Garcia’s insurgent candidacy has won significant grassroots support in Chicago, along with the backing of key labor organizations, including the Chicago Teachers Union and the Illinois Council of the Service Employees International Union.

Both Emanuel and Garcia are Democrats, and Garcia (a former Chicago alderman and Illinois legislator and current Cook County Commissioner) actually has a longer record of running for and winning office on the party line than the incumbent. So opposition to Emanuel in Chicago’s nonpartisan runoff is, as National People’s Action executive director George Goehl notes, based on “a clear set of populist principles, not a party.”

For the most part, however, national Democrats have either backed Emanuel (as did President Obama, who appeared with the mayor in February and has recorded campaign commercials for him) or steered clear of the race. That’s a measure of the political influence maintained by Emanuel, not just in Chicago but in Washington.

Though he was never a favorite of progressive Democrats during his tenures as an aide to Presidents Clinton and Obama, or when he headed the Democratic Congressional Campaign Committee, Emanuel’s stock has fallen since he became mayor four years ago. His decisions to close public schools and to align with corporate interests at a time when the Democratic Party is under growing pressure to address income inequality, wage stagnation and a host of economic injustices has only heightened frustration with the mayor.

That frustration manifested itself in the decision of an old rival of Emanuel, former Democratic National Committee chairman Howard Dean, to back Garcia—as has a group founded by Dean and many supporters from his 2004 presidential run, Democracy for America.

MoveOn.org has also highlighted opposition to Emanuel and support for Garcia.

Yet, few other prominent progressives have joined in making the populist argument against Emanuel.

So the endorsement of Garcia by Sanders is drawing notice in Chicago and Washington. The endorsement mixes local and national political storylines, as Sanders is pondering a possible run for the 2016 Democratic presidential nomination – perhaps as a progressive populist challenger to presumed Democratic frontrunner (and Emanuel-backed prospect) Hillary Clinton.

Sanders will make the endorsement formally on Thursday, at a Chicago event featuring Garcia and Susan Sadlowski Garza, a labor-backed progressive seeking a city council seat on Chicago’s south side.

“I am going to Chicago to support Chuy Garcia and Susan Sadlowski Garza. I support them because we need a political revolution in this country and we need the kind of working-class coalitions that Chuy and Susan are pulling together,” says Sanders,who argues that, “At a time when the wealthiest people and largest corporations are becoming richer while virtually everyone else is becoming poorer, working-class people have got to fight back. And that is what the campaigns of Chuy and Susan are all about.”

The Chicago event caps a week of cross-country appearances by Sanders, who appeared at several large events in Los Angeles last weekend and addressed San Francisco’s Commonwealth Club on Monday. On Tuesday and Wednesday, the senator headed to Las Vegas and then Austin, Texas.

For Sanders, the events are opportunities to speak but also to talk with labor and progressive activists. In Los Angeles, the senator was the keynote speaker at an “awakening our conscience, restoring our democracy” event organized by author Marianne Williamson, which also included on its list of featured speakers Congressmen Alan Grayson and Keith Ellison, former Congressman Dennis Kucinich and author and radio host Thom Hartmann. In Austin, populist writer and commentator Jim Hightower joined Sanders; this writer will MC the Chicago event.

Sanders has said that he will make a decision on whether to seek the presidency later this spring. When we first discussed the prospect a year ago, he explained that such a candidacy would require “a political revolution” – the same phrase he employed when endorsing Chuy Garcia and Susan Sadlowski Garza.

“(When} I talk about a political revolution, what I am referring to is the need to do more than just win the next election. It’s about creating a situation where we are involving millions of people in the process who are not now involved, and changing the nature of media so they are talking about issues that reflect the needs and the pains that so many of our people are currently feeling,” says Sanders. “Essentially, what a political revolution means is that we organize and educate and create grassroots movements, which we certainly do not have right now.”