The president and his wife, fellow Chicagoan Michelle Obama, put their capital behind an enormous campaign to win the Olympics bid. Never before had a U.S. president made such an in-person appeal.
"I urge you to choose Chicago," Obama told members of the International Olympic Committee, many of whom he later mingled with as some snapped photos of him on their cell phones.
"And if you do _ if we walk this path together _ then I promise you this: The city of Chicago and the United States of America will make the world proud," the president said.
Chicago, Rio de Janeiro, Madrid and Tokyo have been making their cases to the IOC for more than a year, but many IOC members were believed to be undecided about which city they would vote for Friday.
By the time the winning bid is announced, the Obamas should be back on a plane to Washington.
The president's whirlwind trip put him in the Danish capital for less than five hours Friday, with Chicago-backers hoping that would be sufficient to give Obama's adopted home town the advantage it needed to win the close, four-way race to become the host city of the 2016 Summer Games.
But the compressed time frame did not shield Obama from Republican criticism that he shouldn't be hopscotching to Europe in Air Force One when there were so many pressing issues to deal with at home.
Asked by a reporter how he thought his pitch went, Obama gave a thumbs up _ and he said the video montage of Chicago during the U.S. presentation made him miss home.
"Obviously now it's up to the IOC members, but we are just grateful for the incredible hospitality," Obama said.
He joked that only one part upset him: "They arranged for me to follow Michelle _ that's always bad."
Both Obamas spoke on deeply personal terms about Chicago, the city at the center of the world's spotlight so many times, including in November when the former Illinois senator won the White House. The president described Chicago as a city of diversity and warmth, a place where he finally found a home.
"It's a city that works, from its first World's Fair more than a century ago to the World Cup we hosted in the nineties," Obama said. "We know how to put on big events."
For all the anticipation surrounding Obama's appearance in Copenhagen, his arrival at the IOC meeting was decidedly subdued.
The 100-plus committee members, who had already been warned not show bias during the presentations, sat silently as the Obamas walked into the Bella Center with the rest of 12-member Chicago delegation.
Mrs. Obama gave a passionate account of what the games would mean to her father, who taught her as a girl how to throw punches better than the boys. She spoke fondly of growing up on the South Side of Chicago, sitting on her father's lap and cheering on Olympic athletes.
She noted that her late father had multiple sclerosis, so she knows something about athletes who compete against tough odds.
"Chicago's vision for the Olympic and Paralympic movement is about so much more than what we can offer the games," she said. "It's about what the games can offer all of us _ it's about inspiring this generation and building a lasting legacy for the next."
The president anchored the U.S. charm offensive.
He referenced his own election as a moment when people from around the world gathered in Chicago to see the results last November and celebrate that "our diversity could be a source of strength."
"There is nothing I would like more than to step just a few blocks from my family's home and with Michelle and our two girls welcome the world back to our neighborhood," Obama said. "At the beginning of this new century,the nation that has been shaped by people from around the world wants a chance to inspire it once more."
In advance of Obama's arrival, Mrs. Obama did some high-powered lobbying for Chicago. The first lady has been in Copenhagen since Wednesday, holding one-on-one meetings with IOC members.
"I'm sure you'd all agree that she's a pretty big selling point," the president told his audience.
After the Obamas' comments, the U.S. delegation fielded questions from committee members, and at one point the president jumped in to answer. He said he envisioned that the Chicago games would allow the United States to restore its image as a place that, at its best, is "open to the world."
He emphasized that the White House and the State Department would put their full weight behind making sure international visitors "feel welcome and will come away with the sense of the incredible diversity of the American people." And Americans, he said, will be reminded of their links to the rest of the world.
Though IOC President Jacques Rogge has said heads of state aren't required to attend the IOC meeting, recent votes indicate their presence can make a difference.
During the 2005 IOC meeting in Singapore, then-British Prime Minister Tony Blair successfully lobbied members on behalf of London's bid for the 2012 Summer Games. Two years later, Vladimir Putin, then president of Russia, helped secure the 2014 Winter Games for Sochi on Russia's Black Sea coast.
Associated Press National Writer Nancy Armour in Copenhagen contributed to this story.