Two expected candidates - Mayor Brandon Johnson and Secretary of State Alexi Giannoulias - have not announced their plans. Others moved quickly to begin gathering signatures and meeting voters.
Susana Mendoza visited a restaurant in Little Village to connect with supporters and launch her petition drive.
"What I always guarantee is that I'll be the hardest worker in anything I set my mind to do," Mendoza said, adding, "I want to be the candidate for mayor that's on everyone's ballot, and in order to do that, I'm not going to leave anything to chance. So, the first minute I'm able to circulate is the first minute I'll start circulating."
Johnson, during his weekly briefing with reporters, said he is not waiting on other candidates before making his decision.
When asked whether he was delaying his announcement to see who else enters the race, he said, "I don't make any decision based upon someone else's, someone else's desire."
He added, "As much as I know that there is this hurry to get to February, I'm in no rush."
Giannoulias could make an announcement this weekend. They would join nine candidates already declared in the race.
Volunteers for candidate Mike Quigley were also out collecting signatures in Lakeview.
Political sources have noted increased activity from social media influencers supporting Johnson. The mayor said he was unaware of any paid promotional efforts, saying, "Quite frankly, it's been organic... and I think it's a testament to how I believe people are responding to this moment."
However, an email shown to ABC7, from Wendee Lee Curtis, who runs the Creator Engagement Program for Johnson's campaign committee, Friends of Brandon Johnson, showed she has been recruiting Chicago content creators. The email said the group is forming a "Content Creator House" with creators who have a combined audience of more than 2.5 million followers.
Johnson downplayed questions about the timing of his reelection decision, saying, "I'm able to skip and whistle at the same time. There will be plenty of time for that."
Candidates for the February municipal election can submit petitions beginning Oct. 19, with a deadline of Oct. 26. Mayoral candidates must collect 12,500 valid signatures, though most gather significantly more to withstand potential challenges.