The opposition is not as visible as the "We Back the Bid" signs plastered across town. But in a city all too familiar with stories of public corruption and problems with public services, there is serious concern the games can only mean more troubles - and bills - for residents.
"I know it's going to cost us money somehow," said Joseph Patrick, a 51-year-old stay-at-home dad. "The government doesn't have a job (so) the only place they can get money is from us."
A new Web site - Chicagoansforrio.com - is the talk of the town and features the game "Match the Olympic host with its estimated budget overrun." About 170 protesters marched outside City Hall on Tuesday night, many insisting that no matter what organizers say, the games will push people from their homes, lead to more corruption and raise taxes.
"I don't believe anything the city and the 2016 committee says," said Larry Rivkin, who grew up in Chicago.
At least one person was later arrested for trying to interfere with workers erecting Olympic symbols in a downtown plaza.
It's not that the bid does not enjoy wide support. Laid-off laborer Dennis Ries, 45, said the Olympics would bring jobs. Resident Molly Mason, 53, sees the games enhancing tourism and public transportation.
"There's no downside, only upside," Mason said.
Others note protests routinely accompany Olympic bids. "The Olympics always galvanizes all sorts of opposition," said A.D. Frazier, chief operating officer for the 1996 Atlanta Games.
In Chicago, though, the opposition seems to be getting stronger.
A poll released this month by the Chicago Tribune showed residents almost evenly split, with 47 percent in favor of the bid and 45 percent against; that's a drop from the 2-1 support the newspaper found in a February poll.
The 2016 bid committee said its own poll last week shows support from 72 percent of Chicagoans. But even that segment has concerns.
Seconds after saying the games in Chicago would be "thrilling," Susan Blaine was wondering what tens of thousands more riders will do to an already overwhelmed public transportation system.
"A Cubs game turns my commute to chaos," said Blaine, 51. "You're belly button to belly button."
For others, concerns about taxes have only intensified since Mayor Richard Daley flip-flopped in April, telling the IOC he'd sign a contract promising the city would take full financial responsibility for the games after long maintaining he wouldn't.
"For a lot of people that was definitely a major moment, when they said, `Wait a minute, we're going to be ... on the hook financially for a very large amount,"' said Anna Tarkov, who writes The Daily Daley blog and opposes the bid.
Organizers have tried to allay such fears, but it can be a tough sell at a time of headline-grabbing corruption cases, the biggest one involving former Illinois Gov. Rod Blagojevich - a Chicagoan accused of trying to sell President Barack Obama's vacant U.S. Senate seat to the highest bidder.
"I just think that the history of corruption sets the stage for a brutal series of events like misuse of funds and insider dealings," said Brian Hayes, 53, of Chicago.
Frazier, of the Atlanta Games, doesn't think the opposition matters to the IOC.
"They will probably be disappointed if there wasn't anything," he said.
Members of a group called No Games Chicago hope he's wrong. They're headed to Copenhagen to tell the IOC that Chicago is in such financial straits that it cannot afford the games and is such a hotbed of political corruption that it doesn't deserve them.
"We are bringing materials to back up our claim that Chicago is not fit to host the games," said Tom Tresser, an organizer for the group.