Democrat Bill de Blasio won New York City’s mayoral election Tuesday by a commanding margin of about 50 percentage points over his Republican opponent, Joe Lhota. De Blasio has promised to alleviate the city’s disparities in wealth. The city’s current mayor, Michael Bloomberg, is stepping down after this term, and de Blasio won the support of many New Yorkers who felt that Bloomberg was only concerned about the rich. De Blasio’s tenure as mayor will be a major test for liberal ideas about governance:

De Blasio’s administration will be a laboratory of sorts for modern progressivism — testing whether an anti-establishment activist can effectively manage a sprawling municipal government and lessen growing inequality between the rich and poor.

“Tackling inequality isn’t easy. It never has been, and it never will be,” de Blasio said in a victory speech at the YMCA gymnasium in his Brooklyn neighborhood of Park Slope. “The challenges we face have been decades in the making, and the problems we set out to address will not be solved overnight. But make no mistake: The people of this city have chosen a progressive path. And tonight we set forth on it — together, as one city.”

But de Blasio also faces a series of immediate challenges as he takes charge of a city government with some 300,000 employees, a $70 billion budget and a dizzying web of intersecting interests. He will have to negotiate several city labor contracts that are due for renewal and overhaul the leadership of agencies, including the New York Police Department, which he has sharply criticized for the anti-crime policy known as “stop and frisk.”

De Blasio also confronts serious obstacles to his tax policy agenda beyond the borders of this overwhelmingly Democratic city, including potential opposition from Democratic Gov. Andrew M. Cuomo and lawmakers in Albany.

Philip Rucker

Meanwhile, in Boston, voters choose Democrat and former labor leader Martin Walsh to succeed Thomas Menino as mayor. Walsh and de Blasio won by espousing a similar kind of liberal egalitarianism:

Both mayors-elect ran instead on a platform of economic opportunity and fairness — an issue that is beginning to resonate more among Democrats at a national level in the wake of the Great Recession. De Blasio and Walsh share a strain of economic populism that echoes that of some of the party’s more liberal members in Washington, like Sens. Elizabeth Warren (D-Mass.) and Sherrod Brown (D-Ohio). . . .

De Blasio outlasted several Democrats with closer ties to business and the city’s financial sector in the Sept. 10 primary, in part by drawing stark contrasts between himself and the policies advanced by incumbent Mayor Michael Bloomberg. De Blasio opposed the city’s stop-and-frisk policy, which Bloomberg championed, and cast himself as a clean break from Bloomberg’s 12 years in office. . . .

Marty Linsky, a former top adviser to Massachusetts Gov. William Weld (R) and a lecturer at Harvard’s Kennedy School of Government, said the slow pace of the economic recovery, which has been especially stagnant in big cities and the Northeast — the unemployment rates in both Boston and New York are higher than the national average — may have fueled an appetite for the sort of activist government both de Blasio and Walsh pledged. And the fact that both men got boosts from labor unions will have political impacts, too.

Reid Wilson

Walsh defeated his opponent, John Connolly, by a much narrower margin of 4 points.