[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/10/01/art.mobamaolym.100109.gi.jpg caption="Chicago-Rio Olympic battle 'close as hell'."]
COPENHAGEN, Denmark (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 heating up, as the two cities battle to host the 2016 Summer Games.
Madrid and Tokyo are also in the running, but sources close the process said that Chicago and Rio have emerged as the clear frontrunners, and are neck and-neck ahead of President Obama's arrival early Friday for a presentation to the IOC's 105 members, who will be voting later that day.
After a flurry of private conversations among IOC officials here, one of the sources close to the process said bluntly that 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 who suggest 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.
Programming Note: CNN Senior White House Correspondent Ed Henry is in Copenhagen with President Obama as he makes a personal pitch to the International Olympic Committee for Chicago to be named the host city of the 2016 Olympic Games. Tune in at 11 a.m. ET Friday as Ed discusses this and much more on CNN Radio’s “44 with Ed Henry.”