CHICAGO — Political newcomer Lori Lightfoot has been elected Chicago mayor, becoming the first black female — and openly gay — leader of the city.
Lightfoot on Tuesday defeated Toni Preckwinkle, a former school teacher who served in the City Council for 19 years before becoming Cook County Board president in 2011.
The 56-year-old Lightfoot is a former federal prosecutor who campaigned on ridding Chicago’s government of corruption. She also said she wanted to help low-income and working-class people she believes have been ‘‘left behind and ignored’’ by Chicago’s political ruling class.
Lightfoot and Preckwinkle were the top two vote-getters in the February general election that saw 14 vie to succeed Mayor Rahm Emanuel. He decided against running for a third term.
Lightfoot will be sworn in May 20.
The race provided voters a clear contrast in a historic runoff already assured of elevating a black woman to lead the nation’s third-largest city.
Chicago is the largest US city to elect a black woman as mayor. Lightfoot joins seven other black women currently serving as mayors in major US cities, including Atlanta and New Orleans.
Lightfoot seized on outrage over a white police officer’s fatal shooting of black teenager Laquan McDonald to launch her reformer campaign. That was even before Mayor Rahm Emanuel announced he wouldn’t seek a third term amid criticism for initially resisting calls to release video of the shooting.
‘‘I’m not a person who decided I would climb the ladder of a corrupt political party,’’ Lightfoot said during a debate last month. ‘‘I don’t hold the title of committeeman, central committeeman, boss of the party.’’
Preckwinkle countered that her opponent lacks the necessary experience for the job.
‘‘This is not an entry-level job,’’ Preckwinkle said repeatedly during the campaign. ‘‘It’s easy to talk about change. It’s hard to actually do it. And that’s been my experience — being a change maker, a change agent, transforming institutions and communities.’’
Joyce Ross, 64, a resident of the city’s predominantly black West Side who is a certified nursing assistant, cast her ballot Tuesday for Lightfoot. Ross said she believes Lightfoot will be better able to clean up the police department and curb city’s violence.
She was also bothered by Preckwinkle’s association with longtime Alderman Ed Burke, who was indicted earlier this year on charges he tried to shake down a restaurant owner who wanted to build in his ward.
‘‘My momma always said birds of a feather flock together,’’ Ross said.
Truly Gannon, a 39-year old mother of four who works as a dietitian, said she wasn’t bothered by stories that portrayed Preckwinkle as an insider aligned with questionable politicians like Burke. She supported Preckwinkle, based on her experience.
‘‘I’m not sure Lightfoot would be able to handle the job like Preckwinkle,’’ she said.
The campaign between the two women got off to a contentious start, with Preckwinkle’s advertising focusing on Lightfoot’s work as a partner at Mayer Brown, one of the nation’s largest law firms, and tagging her as a ‘‘wealthy corporate lawyer.’’
Preckwinkle also tried to cast Lightfoot as an insider for working in police oversight posts under Emanuel and police oversight, procurement, and emergency communications posts under Mayor Richard M. Daley.
In one ad, Preckwinkle criticized Lightfoot’s oversight of the emergency communications in 2004 when a fire killed four children. A judge ordered Lightfoot to preserve 911 tapes after questions were raised about how the emergency call was handled. The ad notes some of the tapes were destroyed, prompting the judge to rebuke Lightfoot. The ad sparked a backlash from the family of three of the children killed, with their sister accusing Preckwinkle of trying to take advantage of her family’s tragedy.
Lightfoot also responded by scolding her opponent for being negative while also airing ads pointing out Preckwinkle’s connection to powerful local Democrats, including one under federal indictment.