Now, he seems an ordinary politician, less the superman of "hope and change" who promised he was going to begin to save the planet from climate change, heal partisan divisions, and make America a proud world leader again.
The challenge for Obama when he addresses his fellow Democrats and the nation this week, political analysts say, is steep: to remind people that progress has been made, even though it may not feel that way, to make the case that the economy would have been worse without his policies, and to ask for more time.
He also must fire up the faithful.
"What concerns me most is the enthusiasm level," said Neil Oxman, a veteran Democratic media strategist. "You know that the angry 55-year-old white man in Columbus, Ohio, is loaded and ready to go," he said, while many Obama backers are dispirited.
He said the president must "try to create some of that magic . . . to deliver the speech he delivered as the keynote at the 2004 Democratic convention. He's got to be mesmerizing."
Adding to the task, Republicans worked last week to widen the enthusiasm gap. At their convention in the crucial, swing-voter-rich I-4 corridor, the straw that stirs the drink in battleground Florida, they portrayed the Mitt Romney-Paul Ryan ticket as serious men with the courage to balance the budget and reduce the debt by making tough choices. Americans want to "put the adults in charge," Ann Romney, the candidate's wife, said during a Tampa appearance outside the convention hall.
That message, with its contrast to Democrats' class-based attacks on the wealthy Romney, could appeal to undecided and independent voters who are looking for solutions. Yet Obama has a powerful asset on his side: Polls show that voters like him despite their disappointment, a reservoir of goodwill upon which he can draw.
Top Obama advisers said Friday that they were not concerned by the GOP convention and would use their own to make the case that the policies advocated by the Romney-Ryan ticket would fatten millionaires and crush the middle class.
"The goal of our convention is to bring the choice in this election into focus," said Stephanie Cutter, Obama's deputy campaign manager. "We don't need to reinvent or repackage the president like the Republicans had to do with Romney."
Even so, much of the promise of 2008 is unfinished, as Romney pointed out in his acceptance speech, an appeal for disappointed Americans to move on from Obama - to "turn the page," as he put it.
Three million more Americans are out of work than in 2008. The national debt has grown by $5 trillion. Partisan gridlock is, to say the least, worse than ever.
Yet Democrats say there are accomplishments to talk about. Obama inherited an economy that was in free-fall after the banking collapse of 2008. His stimulus-spending program and bailout of the Detroit auto industry may have averted a second Great Depression, many economists argue. He won passage of the Affordable Care Act, which expands health coverage to millions, although Republicans want to dismantle the program, calling it a looming fiscal disaster.
The question is whether those feats make a difference in the perceptions and attitudes on Main Street, where people are coping with an official jobless rate of 8.3 percent.
"President Obama will have to convey to the American people how deeply he feels the pain they're feeling," former Pennsylvania Gov. Ed Rendell said, adding that a little humility would go a long way. Filigree like the Greek columns or the fireworks of the 2008 convention - also held in a football stadium - "would be a disaster," Rendell said.
"The president has to acknowledge the state the country is in - that the plans he put in place have worked to an extent, but not enough," the former governor said. "He needs to let the bragging be done by other people, leave it to the surrogates."
David Axelrod, chief strategist for the reelection campaign, said the convention would also be a platform to remind Americans that Romney, who is proposing steep tax cuts, would return the policies that caused the crash - though Axelrod allowed that convention speakers would not dwell on the name George W. Bush.
Undecided voters may have tuned in to the GOP convention looking for details of how Romney would lead the country, but instead got "some snarky lines about the president, some gauzy reminiscences of the past, and some buzz words for the party base," Axelrod argued. "His pitch is, 'I'm a businessman, I've got the secret sauce, trust me.' "
For Democrats, voter apathy - especially among the party's base voters - ranks high on the list of nightmares when it comes to winning a race that polls show is essentially tied. According to a recent national Gallup poll, only 39 percent of Democrats said they were "more enthusiastic" than usual about voting this year, compared to 61 percent in 2008.
Overall, voters like Obama more than Romney. In an Associated Press-Gfk poll taken in late August, for instance, Obama led 51 to 36 percent among registered voters on the question of which candidate cares more about people like you. And 53 percent held a favorable view of Obama, to 44 percent for Romney. Different from job-performance numbers, measures of likability show how candidates are connecting with voters on a personal level.
Analysts say that Obama's advantage in this regard is a major reason the race is so close, despite the sense among voters that things are headed in the wrong direction.
It also explains why the GOP devoted so much of its convention to a parade of speakers attesting to Romney's decency and compassion as a lay Mormon pastor, to humanize him. The party also used its program to celebrate women, mindful of the polling gender gap that is to the Democrats' advantage.
For their part, Democrats will try to push that advantage, with speeches from Elizabeth Warren, the party's Massachusetts Senate candidate, and Sandra Fluke, the Georgetown University law student who became a hero on the left after testifying before a congressional committee on the importance of contraception. (The keynote address will be given by San Antonio Mayor Julián Castro.)
Democrats also will seek to address Obama's polling weakness with non-college-educated white voters - the working class, or so-called Bubba vote.
Who better to help do that than Bubba himself? Former President Bill Clinton will address the convention Wednesday night, making the case for four more years.
Still, conventions go only so far in securing votes, said political scientist and pollster G. Terry Madonna.
"The problem with conventions is that they are not game-changers," Madonna said. "They don't move large numbers of voters permanently. . . . There have been relatively few in American history that have made a difference in the outcome of the election."
Having said that, Madonna noted, the Republicans made a big push last week to include women, as well as minorities, in the hopes of taming criticisms that they were the party of men and the elite.
Madonna said the Democrats no doubt would spend this week trying to dismantle that message.
They will also try to motivate voters like Annie Haey, a Tampa cashier who was riding a train Friday across Florida to see her mother in Miami. "Obama," she said, "needs four more years."
Haey, 57, isn't sold on Obamacare - "I like the president, but I don't want anyone to tell me that I have to take an insurance," she said. As for the Republican challenger: "I don't know his plans, and I don't need to know them. I just don't trust Romney."
Contact Thomas Fitzgerald
at 215-854-2718 or email@example.com or follow on Twitter @tomfitzgerald. Read his blog, "The Big Tent,"
Staff writers Angela Couloumbis and Peter Vanham contributed
to this article.