CHICAGO — Chicago Mayor Lori Lightfoot is fighting for reelection Tuesday after a history-making but tumultuous four years in office and a bruising campaign threaten to make her the city’s first one-term mayor in decades.

Lightfoot in 2019 became the first Black woman and first openly gay mayor of the third-largest U.S. city, and only the second woman to hold the office. But Lightfoot, a former prosecutor and head of a city police review board, now faces serious challenges from multiple candidates, who have hammered her over crime that spiked during the COVID-19 pandemic and a leadership style they say is unnecessarily combative.

With none of the nine candidates likely to receive over 50% of the vote, the race is expected to move to an April runoff between the top two vote-getters. Lightfoot may not be among them.

Lightfoot has touted her record of investing in neighborhoods and supporting workers, such as by increasing the minimum wage to $15 an hour. She also notes that the city has navigated unprecedented challenges such as the pandemic and its economic and public safety fallout to protests over policing.

“The world is very different than it was four years ago. I believe that I’m still the right person and I think the voters will validate that, but we’ve been through a lot,” Lightfoot said after a rally on the city’s west side during the final days before the election. “We can’t go back.”

Lightfoot’s top rivals include Greek-American Paul Vallas, who has run as the law-and-order candidate with support from the city’s police union and promises to put hundreds more officers on the streets, and U.S. Rep. Jesus “Chuy” Garcia, who forced then-Mayor Rahm Emanuel to a runoff in 2015. Brandon Johnson is endorsed by the Chicago Teachers Union, a group that has tangled with Lightfoot, including during an 11-day teachers strike in her first year in office.

If Lightfoot loses on Tuesday, she would be one of the few big-city mayors in recent history to lose their reelection bid. That’s particularly true in the first round of voting, when incumbents generally enjoy an advantage.

But this election is very different, said Constance Mixon, a lifelong Chicago resident and political science professor at Elmhurst University. Of the 10 largest U.S. cities, Chicago is the only place without mayoral term limits, which may make voters in other cities more willing to give an incumbent one more term, Mixon said.

Lightfoot also is the first mayor of a major U.S. city to face reelection following the pandemic, recession and the crime wave that’s occurred in many places, she said.

“I suspect that other mayors — and we’ve got a handful of them that are up this year, but after Lightfoot — are going to face many of the same challenges as Lightfoot,” she said.

Race also is a factor as candidates court votes in the highly segregated city, which is closely divided in population among Black, Hispanic and white residents. Lightfoot, Johnson and five other candidates are Black, though Lightfoot — who is hoping strong support from Black voters will help propel her to victory — has argued that she is the only Black candidate who can win. Garcia, the only Latino in the race, would be Chicago’s first Hispanic mayor, while Vallas is the only white candidate in the field.

Lightfoot has accused Vallas of using “the ultimate dog whistle” by saying his campaign is about “taking back our city,” and of cozying up to the president of the Fraternal Order of Police, whom she calls a racist. A recent Chicago Tribune story also found Vallas’ Twitter account had liked racist tweets and tweets that mocked Lightfoot’s appearance and referred to her as masculine.

Vallas denied his comments were related to race and says his police union endorsement is from rank-and-file officers. He also said he wasn’t responsible for the liked tweets, which he called “abhorrent,” and suggested someone had improperly accessed his account.

But Lightfoot and some of her supporters see some of the criticism of her leadership as motivated by racism, sexism and anti-gay sentiment.

“No other mayor has been asked to change this city within four years,” said city Treasurer Melissa Conyears-Ervin, who is Black, and noted that white mayors like Emanuel and Richard Daley served multiple terms. “When we get in the game, the rules change.”

At a weekend campaign stop, Vallas said he is focused on things like public safety, Chicago’s “demoralized” police department and the number of residents “fleeing” the city’s school district.

“It’s all a product of bad leadership,” Vallas said.

A former city budget director who also led school systems in Chicago, New Orleans and Philadelphia, Vallas lost a 2019 bid for mayor. This time, he has been laser-focused on public safety, saying police officers who left the force under Lightfoot’s administration will return if he’s elected.

It seems to have resonated with voters, such as Antwoin Jackson, who are concerned about an uptick in crime. Jackson said he supported Lightfoot four years ago but cast his ballot for Vallas in Tuesday’s election because he said Lightfoot “did not hold control over the violence in the communities.” Jackson said he feels particularly unsafe when riding public transit.

Johnson, who lives in one of Chicago’s most violent neighborhoods, says more needs to be done to provide affordable housing and social services such as mental health care.

Garcia, a former City Council member, state lawmaker and county commissioner, has called Lightfoot too combative and says he has a record of bringing people together.

The other candidates are businessman Willie Wilson, Chicago City Council members Sophia King and Roderick Sawyer, activist Ja’Mal Green and state Rep. Kambium “Kam” Buckner.