"I'm here," the president said cheerfully at the mid-way point of the faceoff to CNN's Candy Crowley, the debate's moderator, as she tried to keep the red-hot faceoff under control.
Obama's strong performance even prompted the audience of supposedly undecided voters to cheer him at one point, despite being instructed to keep quiet.
Mindful of a dismal debate performance two weeks ago that has helped fuel Romney's ascent in the public opinion polls and turned the presidential race into a dead heat, an energized Obama bounded onstage in Hempstead, N.Y. apparently determined to undo the damage.
He wasted no time taking his first swing at his foe, slamming Romney's economic plan.
"Governor Romney says he's got a five-point plan,'' Obama said.
"Governor Romney doesn't have a five-point plan, he has a one-point plan. And that plan is to make sure that folks at the top play by a different set of rules."
By debate's end, Obama finally mentioned what his supporters maligned him for failing to hammer home during the Oct. 3 sparring match in Denver — Romney's secretly videotaped comments that 47 per cent of Americans are government freeloaders.
"When he said behind closed doors that 47 per cent of the country considers themselves victims who refuse personal responsibility — think about who he was talking about," Obama told the audience.
"Folks on Social Security who've worked all their lives, veterans who've sacrificed for this country .... people who are working hard every day, paying payroll tax, gas taxes, but don't make enough income. I want to fight for them."
Obama faced a high-stakes task as he headed into his second prime-time debate against Romney: to put the brakes on his Republican rival's sudden momentum in a tense, tight race to the White House.
More than 67 million Americans tuned into the pair's opening faceoff almost two weeks ago in Denver. Tens of millions were expected to watch Tuesday's clash to see if a more engaged Obama could make up for his listless initial showing.
Obama vowed to do better — and Democratic pundits said he had to if he hopes to stop Romney from edging past him nationally and in some of the key battleground states that will decide the outcome of the Nov. 6 vote.
He was true to his word. Both CNN and CBS snap polls had Obama winning the debate.
Even on the most dangerous question posed to the president — about his administration's handling of the crisis in Libya — Obama tidily disarmed a flailing Romney.
Contrary to recent suggestions from Republicans that the president was allowing Secretary of State Hillary Clinton to take the blame for the response, Obama said he bears full responsibility.
"Secretary Clinton has done an extraordinary job," he said. "But she works for me. I'm the president. And I'm always responsible."
That lead to the most painful moment of the showdown for Romney, when he insisted — falsely — that the president failed to immediately characterize the attack on the Benghazi consulate last month as an act of terror. The violence resulted in the deaths of four Americans, including Chris Stevens, the U.S. envoy to Libya.
"Check the transcript," Obama told Romney as he continued to assert that it took the president two weeks to describe the Benghazi attack as terrorism.
In a moment that almost instantly prompted a conservative social media uproar, Crowley also weighed in to correct Romney as he visibly blanched. In fact, she told him, the president called it such in a Rose Garden appearance the day after the violence.
Obama, meantime, chided Romney for attempting to politicize the events, glowering at his opponent as he delivered his stern rebuke.
"The suggestion that anybody on my team — the secretary of state, our U.N. ambassador, anybody on my team — would play politics or mislead when we've lost four of our own is offensive, governor," he said as the audience disobeyed instructions to stay silent by cheering the president.
It wasn't the only bad moment of the showdown for Romney. He referred to "binders full of women" when detailing his efforts to hire more female employees as Massachusetts governor, a phrase definitely not destined for a Republican campaign ad.
Although both men attempted to talk over Crowley at various points in their duel, Romney also appeared peevish as he repeatedly complained about the questioning format. As well, he strode uncomfortably close to Obama, including as he chastised the president for failing to greenlight TransCanada's Keystone XL pipeline.
"How in the world the president said no to that pipeline, I'll never know," Romney said.
But he also had his own moments of strength, particularly when he asked Americans if they were better off than they were when Obama was elected four years ago.
"We just can't afford four more years like the last four years," Romney said, accusing Obama of failing to keep promises on overhauling entitlement programs and dealing with illegal immigration.
"This is a president who hasn't done what he'd said he'd do. The middle class is getting crushed under a president ... who doesn't understand how to get the economy working again."
Both men faced a barrage of questions from audience members on everything from women's issues immigration and taxation proposals.
Obama delivered one of his most devastating hits when mocking Romney's lack of detail on how he'll create jobs, lower taxes and increase military spending while cutting the mammoth national debt.
In fact, the president charged, Romney's promises would cost US$7 trillion.
"If somebody came to you, governor, with a plan that said: 'Here, I want to spend seven or eight trillion dollars, and we're going to pay for it, but we can't tell you until maybe after the election how we're going to do it,' you wouldn't have taken such a sketchy deal," he said.
"And neither should you, the American people."
He also mocked Romney's response to the opening question from a 20-year-old college student worried about whether he'd be able to find a job once he graduated.
Rather than advocating job creation, Obama said, the Michigan-born Republican once said "we should let Detroit go bankrupt."
Romney denied the charge, adding Obama actually did, for all intents and purposes, take the automakers "to bankruptcy."
Obama scoffed at that suggestion, calling it untrue. Indeed, throughout the debate, the president accused Romney several times of saying things that were "absolutely not true."
Women's issues came into sharp focus during the debate, with Obama defending his record on equal pay for equal work and easier, more affordable access to contraception under so-called Obamacare, his sweeping health-care overhaul.
He mentioned several times that Romney wants to cut funding to Planned Parenthood,
Romney, meantime, said "women have lost 580,000 jobs" under Obama and argued he's a better choice for all Americans on election day, including women.
Some recent polls have suggested Romney, who has espoused more moderate positions over the past two weeks, has all but erased Obama's advantage among women over the past 12 days.
Women have long been Obama's demographic shield against the Republican, and Democrats are particularly nervous about any suggestion he's losing female voters. The Obama campaign has raised questions about this week's USA Today/Gallup poll that suggested the president's lead among women had evaporated, calling it a flawed "outlier" that bears little resemblance to other swing state surveys.
With the race all but tied, the debates are proving crucial, providing each campaign with the potential for a breakout moment as the clock winds down on the campaign.
Early voting is already in full force in 43 of 50 states — including key battlegrounds like Ohio and Iowa — and both Obama and Romney are running out of time and opportunities to soar, or to recover, from their debate performances.
The campaign's final debate is next Monday in Boca Raton, Fla. That bout will be focused solely on foreign policy.