The IOC will release its evaluation commission report on Wednesday, exactly a month before the vote in Copenhagen on Oct. 2, marking another milestone in the two-year global campaign.
The report won't grade or rank the candidates — Chicago, Madrid, Rio de Janeiro and Tokyo. It will focus on technical criteria such as venues, budgets, transportation plans, accommodation, security and government and public support.
With IOC members still barred from visiting bid cities in the wake of the Salt Lake City scandal, the report is intended to offer guidance to the 100-plus delegates when they cast their secret ballots next month.
The evaluation may play only a minor role, however, as members tend to vote for individual reasons, including geopolitical factors. The final presentations on the day of the vote are also considered crucial.
Still, a glowing review in the evaluation report can provide valuable momentum in the final stretch, while a negative assessment can all but kill a bid.
"It could be very important," said Gerhard Heiberg, an IOC executive board member from Norway. "At this stage there is no front-runner and no one lagging behind. All are on an equal basis. The report will be studied by IOC members perhaps more than before."
The first IOC evaluation report made public was in 1993 during the bid process for the 2000 Olympics, which were awarded to Sydney. Some members have been critical of the reports for merely listing statistics and not making clear which bids are better than others.
"Unless you were a cryptographer of some sort, in the past it's been impossible to find out what the opinion of the commission was as to the suitability of each candidate," senior Canadian member Dick Pound said. "It's not enough just to report what the cities said. The report should say, 'We recommend the following candidates in this order for these reasons.'"
The four candidates, meanwhile, are hoping to make a good impression in the report, which is based on visits to the four cities by the evaluation commission earlier this year.
Chicago, seeking to bring the Summer Olympics back to the United States for the first time since the 1996 Atlanta Games, has been promoting its plan for holding compact games on the downtown lakefront.
"The evaluation report is a very important step in this process," bid leader Patrick Ryan said. "It will hopefully give the entire membership a snapshot of the city that the evaluation commission visited. As the least well known of the four cities hopefully the full membership will have a better understanding of the type of games Chicago would offer after this report comes out."
Tokyo, which held the Olympics in 1964, will have a new prime minister behind the bid after Taro Aso's Liberal Democrats were voted out of office by the Democratic Party over the weekend. The likely next prime minister, Yukio Hatoyama, has voiced support for the bid.
Tokyo bid leader Dr. Ichiro Kono said the level of government support remains the same and maintained the Japanese capital has the strongest financial guarantees during a time of global economic downturn.
"We offer the safest, securest, most risk-free and most dependable bid," Kono said. "This is especially critical considering today's uncertain environment."
Madrid, which is bidding for the second straight time after losing to London in the race for the 2012 games, believes it is well placed.
"We have worked extremely hard on every aspect of our bid and all the hard yards have put us in a strong position for the final run to the finishing line," bid leader Mercedes Coghen said. "We believe we are in a good position to win but there is no room for any complacency. It is still all to play for."
Rio de Janeiro has made a strong case to take the Olympics to South America for the first time.
"We await this report with a little bit of anxiety but confident as well," bid chief executive Carlos Roberto Osorio said. "We think we have a very strong technical project. We are confident that our message is getting through clearly to the IOC members."
According to Pound, all that may not matter yet.
"I would say that all the candidates have been working hard at generating a sense of excitement and momentum, but all that exists only in their own minds at the moment because nobody has actually voted," he said. "You have to learn to separate the promotional material from the fact."
What may prove decisive is the appearance in Copenhagen of government leaders. Brazilian President Luiz Inacio Lula da Silva and Spanish King Juan Carlos have announced they will be going. Tokyo has invited Crown Prince Naruhito. The big question is whether President Barack Obama will lobby for Chicago.
"Olympic bids these days are so important to the countries that it would be surprising for a country not to send its biggest hitter," Pound said. "If the U.S. doesn't match the others, that's something that will be noticed."