CHICAGO — Cook County Commissioner Brandon Johnson will run for Chicago mayor, adding another progressive challenger to the field of 2023 candidates and raising the prospect of a rematch between the Chicago Teachers Union and Mayor Lori Lightfoot.

Johnson’s announcement early Thursday is not a surprise. At a recent forum in Logan Square for progressive contenders, Johnson repeatedly said “when I’m mayor” in response to questions and he has long been considered a possible candidate for the post. Johnson, a longtime CTU leader, first won public office in 2018, when in the Democratic primary he defeated Cook County Commissioner Richard Boykin, who earned the ire of organized labor by voting against the county’s soda tax.

In a release formally announcing Johnson’s candidacy, he highlighted his background as a teacher and held a news conference later Thursday near Jenner School, where he started his career in education before Jenner merged with Ogden International School.

“As a teacher, I experienced the painful impact of disinvestment on my students and their families, and this personal experience — seeing children endure inequity — is what fuels my commitment to building a stronger, safer and more equitable Chicago,” Johnson said.

His entry into the race potentially complicates the political calculus for U.S. Rep. Jesus “Chuy” Garcia, who is also considering a run for mayor. Garcia was the teachers union’s chosen candidate in 2015 and helped push Mayor Rahm Emanuel into the city’s first runoff. Although Garcia has much higher name recognition among Chicago voters, he would have to find backing elsewhere if he enters the race.

In an interview with The Chicago Tribune Thursday, Johnson said Garcia “40 years ago, laid some groundwork for the moment that we’re experiencing right now,” but Johnson added that “progressives in this city have aligned themselves with the progressive candidate,” and they have decided that he best reflects their desires.

Talks are ongoing with the local Service Employees International Union chapter, one of the city’s other most powerful progressive unions, Johnson says. Both SEIU and CTU lined up behind Cook County Board President Toni Preckwinkle’s mayoral bid in 2019.

“These workers are my colleagues, I served alongside them in school buildings, I’m one of them. These are family conversations,” Johnson said.

In Johnson’s time on the county board, he’s pushed a measure making it illegal to refuse to show or rent property to people with certain criminal records. He also drafted a symbolic resolution that supported diverting money from policing in the wake of nationwide protests demanding police budgets be defunded.

Lightfoot’s campaign aimed to portray Johnson as a one-note candidate.

“There’s no shortage of ambitious politicians trying to advance their own career right now, and we’ll put up Mayor Lightfoot’s progressive achievements versus Brandon Johnson’s thin resume any day of the week,” the Lightfoot camp said in a statement following Johnson’s announcement. “In the case of Johnson, his campaign stands on one platform and one only: to defund the police department entirely. It’s easy to talk about what you would do — it’s another thing to be in the arena, doing the work every day to keep our city moving forward.”

Johnson said such comments are “typical from the mayor. She has a very narrow view of the world, doesn’t understand that my work predates the fact that I’ve just been a Cook County commissioner.” He cited his time as a teacher and an organizer with CTU, where he worked on the successful campaign to bring an elected school board to Chicago, to boost funding to CPS and the 2012 strike. Lightfoot’s response “shows you how disconnected she is with working people ... (and) the fact that she’s intimidated by the work. And it’s why her workday’s going to end in a few months.”

Johnson has long been a critic of the city’s political establishment. At the recent forum, for instance, the candidates were asked about how to make Chicago a place where Black residents can thrive.

“Can we just be honest? They don’t want Black people here,” Johnson said, before listing policies he says drove that population out, such as demolishing public housing and closing schools. “And every administration has been willing to do that, whether it’s calling for ‘shoot to kill’ or raising bridges. It’s a wicked and unjust system.”

Johnson enters a crowded field that includes Lightfoot, Ald. Sophia King, activist Ja’Mal Green, Ald. Roderick Sawyer, former CPS chief Paul Vallas, state Rep. Kambium “Kam” Buckner, Ald. Raymond Lopez and businessowner Willie Wilson.

Earlier this fall, Johnson, a former social studies teacher, picked up the endorsement of the CTU, which contributed $59,900 to Johnson’s political fund. The Illinois Federation of Teachers has said it would provide him with $1 million for his race.

Asked how he would balance the interests of the CTU with the city’s, he told the Tribune that while he would bring “all sectors together,” there is “no conflict of interest” involving the union. “How is it that if you’re part of a labor movement that you miss the fact that we’re also taxpayers and that we’re parents?”

Johnson’s entry into the race presents a significant challenge for Lightfoot, who has long wrangled with CTU and other progressive heavyweights during her first term. She presided over an 11-day strike teachers’ strike in 2019 and multiple rounds of standoffs with the union during the COVID-19 pandemic over her plan to return to in-person schooling.

Lightfoot has also placed herself at odds with progressives over criminal justice, refusing to cater to the “defund the police” movement following the 2020 murder of George Floyd and often criticizing Cook County courts for what she said was a lack of consequences for violent offenders.

While many progressives will oppose her candidacy, Lightfoot will also try to argue that she’s been a progressive mayor.

Although she abandoned some high-profile promises supported by progressives, such as the elected school board plan that passed in Springfield, she has quietly built a strong relationship with some labor leaders who appreciate her record on worker issues.

In her first few months as mayor in 2019, Lightfoot pushed through the fair workweek ordinance that requires large Chicago employers to give workers at least two weeks’ notice of their schedules and compensate them for last-minute changes. Later that year, Lightfoot passed her first budget, which set the stage for a $15 minimum wage long sought by local unions.

She reached a compromise with aldermen to create an elected civilian police oversight agency — albeit with far weaker powers than she campaigned on — and closed loopholes in Chicago’s Welcoming City ordinance to prohibit police from cooperating with federal immigration authorities to deport immigrants living in the country without legal permission who have criminal backgrounds.