The Obamas hope an appearance in Copenhagen will boost their chances of bringing the Olympics to Chicago.

Ed Henry
CNN

As First Lady Michelle Obama and talk show host Oprah Winfrey wrapped up a day of furious behind-the-scenes lobbying of International Olympic Committee members here, two sources close to the process tell CNN that the battle between Chicago and Rio is privately heating up over who will host the 2016 Summer Games.

Madrid and Tokyo are also in the running, but the sources close the process said that Chicago and Rio have emerged as the clear front-runners and are in a neck-and-neck battle ahead of President Obama's arrival early Friday for a presentation to the IOC's 105 members who will be voting later in the day.

After a flurry of private conversations among IOC officials here, one of the sources close to the process said bluntly it's "close as hell" between Chicago and Rio as both Obama and Brazilian President Lula da Silva plan to make personal appeals to the voters on behalf of their cities on Friday morning.

In a sign of just how ferocious the lobbying is, King Juan Carlos of Spain and new Japanese Prime Minister Yukio Hatoyama are also making personal pitches to the IOC members.

Despite widespread speculation that Obama is only flying all the way to Copenhagen for a four-hour lobbying mission because the White House has gotten a private heads-up that Chicago will win and he should come to claim victory, the sources close to the process insisted that the voting has not been pre-cooked so Obama is swooping in at some political risk because it is unclear that the U.S. bid will be successful.

Chicago Mayor Richard Daley, who is already here in Copenhagen, has been privately giving the White House positive progress reports about what he's hearing from IOC members suggesting the U.S. bid is in good shape, according to the sources close to the process. But the sources cautioned that Obama and top aides are only cautiously optimistic and want to wait until the actual voting before they contemplate any celebrations.