As a Boston mayoral candidate, she had plenty of opportunity to pivot away from her more liberal ideas. She didn’t, and it paid off.Michell Wu is the first woman and the first person of color to be elected mayor of Boston.M. Scott Brauer for The New York TimesBOSTON — For progressives, Tuesday’s elections brought a litany of bad news and one conspicuous bright spot: Michelle Wu, the newly elected mayor of Boston, who took the stage in a scarlet dress, carrying her 4-year-old son on her hip.Ms. Wu, 36, was in intense campaign mode this summer when Eric Adams won the Democratic primary in New York, convincing many pundits that the progressive movement was sputtering at the ballot box, dampened by the practical concerns of older, moderate voters.Ms. Wu had time to pivot toward the center, but she did not: Right up until its last weeks, her campaign was built around an agenda that galvanized this city’s young left, like fare-free public transit, climate action and rent control.And that did not seem to hurt her, even with centrist voters. In Tuesday’s election, Ms. Wu trounced a more moderate opponent, City Councilor Annissa Essaibi George, by a 28-point margin. Between the September preliminary election and Tuesday’s general election, she expanded far beyond the younger, more educated whites who are her base, winning by commanding margins among Black, Latino and Asian voters.Still flushed from her victory, Ms. Wu affirmed her plan to make the city into a laboratory for progressive policy, the kind she studied under her mentor Senator Elizabeth Warren.“Boston has come together to reshape what is possible,” she told supporters. “We are the city of the first public school in the country, the first public park, the first subway tunnel. We are the city of revolution, civil rights, marriage equality. We have always been that city that punches above our weight.”Ms. Wu was supported by Senator Elizabeth Warren, a national progressive leader.Philip Keith for The New York TimesMs. Wu’s campaign — and particularly her “years of infrastructure building and engagement” — should be a model for progressive candidates across the country, said Adam Green, co-founder of the Progressive Change Campaign Committee, which endorsed her.“She doesn’t just represent transformational ideas in a vacuum; she was someone who built credibility in the local community over the years,” he said. “We’ve lost races when the candidates swing out of nowhere, and the first time people are hearing of them is when they run for office.”One explanation for her success is Ms. Wu herself, who is difficult to caricature as a radical.Over her four terms as a city councilor, Bostonians have gotten to know Ms. Wu as soft-spoken and thoughtful, intensely focused on policy, meticulous about showing up at meetings and returning phone calls. That experience acted as a “buffer,” if any was needed, “for someone this progressive to be elected mayor,” said David Paleologos, director of the Suffolk University Political Research Center.“That kind of quiet, methodical style is a new style for progressives,” he said. “It’s a different kind of style that she has invented.”Lydia Chim, 26, a budget analyst who moved to Boston from California, said Ms. Wu struck her as experienced and practical, qualities she does not always find in progressives.“It’s a refreshing thing to see a progressive candidate who really knows how to get things done,” she said.Ms. Wu also cultivated relationships with the city’s conservative power centers, tapping into her Harvard pedigree and post-college experience as a management consultant and small-business owner. She comes across as “somebody who is very clearly into managing systems,” which has helped her build trust in those parts of the city, said Jonathan Cohn, the chair of a local Democratic committee and a progressive activist.“Her career is where it is because she has done a good job of catering to business owners and progressives at the same time,” he said.Ms. Wu has also benefited from some conditions outside her control.The demographics of Boston are changing rapidly, with young professionals drawn to the city for jobs in technology, medicine and education. Boston has become “an intellectual elite city,” said Nan Whaley, the mayor of Dayton, Ohio, and the president of the U.S. Conference of Mayors. Its politics, she said, are changing accordingly.“Boston might be a harbinger for the situation in our big cities,” she said. “They are expensive to live in. People are more educated. That might be a difference we will see.”It helped that the popular incumbent, Mayor Martin J. Walsh, was tapped as the federal labor secretary in January, leaving the Boston race wide open. By then, Ms. Wu was four months into a campaign against Mr. Walsh, criticizing his administration for insufficient action to combat racial injustice and climate change.In open races, it is not unusual for voters to opt for a candidate who has characteristics the previous mayor did not, said David Axelrod, a Democratic political consultant.Takeaways From the 2021 ElectionsCard 1 of 5A G.O.P. pathway in Virginia. More