Air Force One landed at O'Hare Airport just before 6 p.m. It will be a quick trip to Chicago -- his 10th since taking office -- for Obama, who arrives Wednesday evening and leaves later that same night. Tickets to the event -- which includes performances by Chicago's Jennifer Hudson, Herbie Hancock and OK Go -- range from $50 to $35,800.
"Because of the 50th birthday, that makes the day extra special. And I think when you put that together with the tremendous lineup of talent that they have, it's one of those events that's not to be missed," Pedro DeJesus, Jr., said. He paid $200 for a ticket.
About 100 VIPs will have dinner and a photo op with the president, who joked about turning the Big 5-0.
"I'm going to get advice from some around the table about how to handle this milestone," President Obama said.
"I'm quite a few years older than the president. I can tell him, if you're happy and healthy, that's more important than a number," said U.S. Sen. Dick Durbin, (D) Illinois.
Vincent Casillas is one of several event hosts who will work the crowd inside the Aragon. He said Obama's campaign staff purposely chose the Aragon over a ritzy downtown location.
"The president also knows that where he started is where he wants to make sure people know he's still at, and that's at the ground level, talking to people, rubbing shoulders with people," Casillas said.
Uptown resident Laurie Heffernan said the preparations around Aragon have been going on all week. "Given that it is the most diverse neighborhood in Chicago, I think it is an awesome place for him to celebrate," Heffernan said. "Secret Service has been here- I've seen them every day since Wednesday... I've seen the trucks with the portable air-conditioning because the Aragon doesn't have air-conditioning,"
The event also brings big time White House-style security to the neighborhood. The Secret Service closed a two-block radius around the venue and the CTA's Lawrence el stop will be closed from 5:30 p.m. to 9:45 p.m. Wednesday.
"Some of the residents around here may complain, but people understand, you know, under the circumstance." Sherron Ingram, Uptown resident, said.
"I know it's going to be hard getting home, but I'm really excited that he is going to be a few blocks away," Chris Moses, Uptown resident, said.
Obama's birthday bash is also drawing demonstrators, including activists who say the president has ignored the immigration issue.
"We are here to remind him that he made promises to us. That's why we voted for him," said Fabian Morales. "We are asking President Obama to stop the deportations."
Obama campaign donations, ratings lower
The birthday bash comes just a day after the president signed the debt deal, which raised the federal debt limit and kept the U.S. from default. That debt crisis almost led Obama to cancel his Chicago trip and fundraiser.
Those negotiations did cancel several other major fundraisers and his campaign said it expects to raise of tens of millions of dollars less this summer.
"I think it's just a temporary blip. It's not going to have any long-lasting impact on the campaign at all," John Rogers, Obama 2012 fundraiser, said.
Lower approval ratings for Obama
Those recent negotiations aren't doing much for Obama's efforts either.
"I think most people see Obama as really trying to get something done that was important. The downside is that he didn't seem too powerful enough to get it through easily," said Dick Simpson, UIC political science dept.
Obama's approval ratings have fallen to 42 percent. But experts say you can't take too much from those polls. Ronald Reagan had similar ratings at the end of his first term and went on to win re-election. George H.W. Bush had the highest ratings of any president and lost to Bill Clinton at re-election.
"Even though people may be upset right now, it does not mean that these people will vote against Obama and for the Republican candidate," said Laurel Harbridge, Northwestern University.
Political fundraising operations typically slow down in the summer because many donors are on vacation and high-dollar events don't usually resume until after Labor Day. During his first presidential campaign, Obama raised about $21 million in the summer of 2007, compared with about $33 million in the spring of that year.
Jim Messina, Obama's campaign manager, said the campaign had not yet set a revised goal for the current fundraising period ending Sept. 30 but would urge "grass-roots fundraisers" to step up their efforts in the weeks ahead. The campaign has emphasized its large donor base -- more than 550,000 people gave money during the spring -- and it plans to lean heavily on small donors in August and September.
"We're going to be very aggressive in trying to find ways to engage the grass roots," Messina said. "We always said ... they're the biggest piece of this and they own the campaign and we're about to give them an even tougher assignment."
Romney released youtube video
Republican presidential hopeful Mitt Romney is using Obama's trip to Chicago as a chance to discuss the city's unemployment rate, which he said has jumped 48-percent since Obama's election. That video, "Obama Isn't working: Chicago," is posted on youtube.com.
Chicago Mayor Rahm Emanuel, who once served as Obama's White House chief of staff, defended his former boss.
"When he was governor, Massachusetts was 47th out of 50 in job production. In case he forgot that, I'd like to remind him of that," Emanuel said of Romney.
Mayor Emanuel said the economy would be even worse had Obama taken Romney's advice and let the auto industry go bankrupt. But Republicans say it is today's economic numbers that count. And Obama and the Democrats should be more concerned about that than raising money for reelection.
"There's nobody better at raising money, but they're just not very good at managing economy and i think that's what is more important to most people," Pat Brady, Illinois Republican Party chairman, said.
While Republicans say Obama should spend his time managing the economy instead of fundraising, political experts say a bad economy only helps Republicans in 2012.
"Presidents win reelection or lose reelection on the economy more than any one thing. If economy continues to limp along, Obama is going to be in big trouble this time next year," said Wayne Steger, DePaul University Political Science Dept. chairman.
Which could translate into fundraising dollars, although, so far not much money is flowing to any candidate.
"Everybody is just holding their dollars on both sides. Look for the money to start flowing much more next year," Steger said.
The Associated Press contributed to this report. All rights reserved.