Continued from page 1

Chicago’s organizers will make their final presentation to IOC officials on Friday morning, with the other bidding cities to follow. IOC members will then vote in as many as three rounds, eliminating the lowest-scoring city each round. The first city to capture at least 50 percent of the vote will win.

Past votes suggest the contest will go down to the wire. London and Sochi each won in the final round of voting by a mere four votes. Sydney, Australia, was awarded the rights to the 2000 Summer Olympics by two votes in the final tally, despite badly trailing front-runner Beijing in the first three rounds.

“Obama will matter a lot, definitely, especially since it’s so close,” said Rob Livingstone, the producer of, a Web site devoted to the Olympic bid process. “Any edge you can get is very important.”

Predicting an IOC decision is inherently challenging, and recent technical evaluations of the bids offered few clues on the committee’s leanings. The IOC had been critical of Chicago’s inability to get a full financial guarantee from the federal government to protect against cost overruns, but those concerns were addressed earlier this month when the Chicago City Council passed a measure ensuring a full financial guarantee at the local level.

All four cities have mounted strong public relations campaigns touting the technical side of their bids, but Olympic observers said emotional arguments often play a bigger role. Some give the edge in Copenhagen to Rio de Janeiro because IOC members might be moved by the notion of holding an Olympics in South America for the first time. Brazil has also played up its high level of support from its citizens.

But analysts said Mr. Obama’s presence will boost Chicago’s profile.

“What Chicago can use to their advantage is to say that President Obama calls Chicago his hometown and they could try to, in the presentation, use the emotion and swing the votes their way,” Mr. Livingstone said. “The final presentation is going to be very, very important to the final results of this election.”