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The report highlights the pros and cons for all of the cities involved: Chicago, Madrid, Rio de Janeiro and Tokyo.
The in-depth analysis on each of the 2016 Candidate Cities reveals concerns about Chicago's mass transit system, Tokyo's public support for bringing the Games to Japan, Madrid's organization skills, and Rio de Janeiro's ability to accommodate millions of additional visitors.
The International Olympic Committee's evaluation team says the Chicago plan would turn the city's center into an "Olympic playground."
Their just published report has plenty of positive comments but some are mixed with concern.
"As they've raised issues, there's nothing in there we can't resolve," said Patrick Ryan, Chicago 2016 Chairman.
The IOC says Chicago's "budget is ambitious but achievable." However, it seems to take issue with Chicago's plan to build many temporary venues including the main Olympic Stadium and aquatics center in Washington Park. Chicago is doing it to save money and avoid leaving behind large facilities that would go unused and be a burden to taxpayers.
The IOC's official policy is that cities should "build a new venue only if there is a legacy need." But later in the report they say "the emphasis on major temporary or scaled down venues increases the element of risk."
Chicago 2016 is betting the IOC won't want any white elephants.
"We have very high confidence in our ability to deliver high quality temporary venues," said Doug Arnot, Chicago 2016 Venue Operations.
The International Olympic Committee is also concerned about traffic and congestion, especially around McCormick Place. They question whether the expected two million Olympic visitors will be able to get around quickly and efficiently.
Metra, the report says, simply couldn't handle a doubling in the number of daily riders. If extra trains can't be found, spectators would be asked to take the bus, albeit by way of Olympic express lanes.
"I think the transportation issue is overblown a bit. Chicago's biggest competitor is Rio and the IOC used the term critical when it assesses need for Rio's transportation improvements," said Carson Cunningham, Olympic historian.
"If we should find we weren't able to absorb what we've anticipated on Metra we can reallocate that to park and ride lots and increased bus system," said Arnot.
The IOC report raves about the proposed Olympic Village, calling the lakefront location well-designed, saying it will create a "special experience for athletes."
The IOC also sampled public opinion in each of the candidate cities:
- 85 percent of residents in Rio and Madrid say they want the Games
- 67 percent of Chicagoans told IOC pollsters they want the Games
- Tokyo had the lowest level of public support: 56 percent
A new poll out on Wednesday night, however, finds support for hosting the 2016 Games has dwindled in Chicago.
The Chicago Tribune/WGN poll found support now stands at 47 percent, down from 61 percent in February.
All in all, bid Chairman Pat Ryan says he's happy with Chicago's position going into the final month.
"We'd like to come up strong on the outside, do a Michael Phelps and go over the opposition and touch before they do," said Ryan. Read the Chicago 2016 reaction
Rio: Chicago's competition?
Many believe Rio is Chicago's biggest competitor. The Brazillian city with its plans to build new rail lines, an airport and re-generate poverty ravaged areas, faired remarkably well in the IOC report.
Rather than referencing an annual murder tally that reaches into the thousands, IOC evaluators wrote: "Rio de Janeiro recognizes that it faces safety challenges."
Sports industry consultant Marc Ganis says while Rio offers lofty goals, the IOC's appetite may not be that big.
"It's not that easy and it's incredibly expensive and it gets blamed on the Olympics. They don't like that," said Ganis.
An IOC poll conducted in February found Rio and Madrid with the highest support among local residents for hosting the Games. Sixty-seven percent of Chicagoans told pollsters they want the Olympics here.
Some call Chicago a front runner, but not the city's bid chief whose worried about rubbing IOC members the wrong way.
"I've never seen a group more sensitive to arrogance," said Ryan. "They don't take very well to someone thinking they got it wrapped up."
Decision day: October 2
The final decision on the 2016 host city will be made by the IOC on October 2 in Copenhagen.
The report was written based on four-day visits to each of the host cities between April 4 and May 8. Chicago was the first of the four to be visited.
For nearly a week in early April, Chicago's bid team sat face-to-face answering hundreds of questions from the International Olympic Committee evaluators before taking them on an 11-hour tour of the city's proposed venues.
The report is the result of that visit, and others just like it to Rio, Madrid and Tokyo.
"The bid is a strong one, but at the end, there is only one winner," said Nawal El Moutawakel, IOC Evaluation Commission Chair.
The Associated Press contributed to this report.