Brewer, a South Side native with degrees from Harvard, Stanford and Yale, said his decision follows months of conversations with residents who feel disconnected from city leadership.
"Over the last year, I was running the CHA, and during that time I had conversations with hundreds of people. And there was this recurring feeling, this recurring theme that ran through all those conversations of people not feeling seen and heard," he said.
The announcement comes after a turbulent period between Brewer and Johnson. Earlier this year, Johnson attempted to remove Brewer as CHA Operating Board chairman in a dispute that became public. Brewer said that experience shaped his view of city government.
"I had a front-row seat to some of the dysfunction happening at City Hall while leading the CHA, but the CHA is just one example," he said.
Brewer insisted his candidacy is not about settling scores.
"This is not a spite campaign, nor is this a spoil, an attempt to spoil the race. I'm running to be the mayor of Chicago," he said.
His campaign launch video emphasized his personal story and message of opportunity.
"I'm living proof that where a pin drops on a map, doesn't have to determine where you end up," he said in the clip.
Brewer's entry comes one day after a new poll showed twothirds of Chicagoans disapprove of Johnson's job performance. Brewer said the numbers reflect broader frustration.
"We have a broken city in a lot of ways. It's hard for businesses; it's hard for individuals. It's hard for communities, and I think that poll reflects that change is needed," he said.
Johnson, who has not yet announced whether he will seek reelection, dismissed concerns about vulnerability.
"Look, my priority is building safe and affordable communities. Look, the politics and the naysayers, I believe a few years ago, I think I was polling at 2.2%," he said.
Brewer also pushed back on Johnson's continued calls to raise taxes on wealthy residents and businesses.
"If the main source of revenue is taxing businesses, then taxing businesses more. Then, we've failed," he said.
Brewer said the stakes for the city are high.
"I have experienced the best and the worst of Chicago, and we're now at a turning point, where our decisions over these next four years will impact the city for the next 40 years, and so I decided to jump into the race to move Chicago forward without leaving people behind," he said.
In discussing the ongoing Chicago Bears stadium saga, Brewer said the city needs a unified approach with Springfield to keep the team from moving to Indiana. He also noted he grew up liking both the Cubs and the White Sox, but now considers himself a Sox fan.
Though he enters the race as an underdog, Brewer said he is ready to compete.
Democratic Congressman Mike Quigley will launch his mayoral campaign Saturday in Uptown.
And George Cardenas, Susana Mendoza and Maria Pappas are running.
Illinois Secretary of State Alexi Giannoulias is expected to jump in the race.
And newcomers Liam Stanton and Joe Holberg are on the list, too.