Although Romney is still trailing badly in the polls, especially in the crucial swing states, his strong showing lifted conservative morale with more than four weeks left to turn the campaign around.
The two sparred mainly over the economy, in particular tax, jobs and health care during a statistics and policy-laden 90-minute debate that was expected to draw an audience of more than 50 million.
Romney was forceful from the start, accusing Obama of repeatedly portraying his policies as inaccurate, and he maintained that momentum throughout. Obama, looking tired and at times irritated, remained largely calm.
In the spin room afterwards, Romney's campaign team hailed it as a victory. Eric Fehrnstrom, Romney's campaign spokesman, could not contain his glee.
"Governor Romney clearly won," he said. "If this was a boxing match, the referee would have stopped it." He predicted it would be "a close race".
David Plouffe, one of the architects of Obama's victory in 2008 and a senior member of his campaign this year, was subdued. "We are going to come out of this debate okay," he said, adding that the Romney team had needed a game-changer and this was not one.
Another of Obama's campaign team, Stephanie Cutter, insisted Obama had won the debate on substance but, unusually for this tough spokeswoman who normally gives little ground, she admitted Romney had won for style and preparation.
A CNN flash poll of registered voters had 67% saying Romney had won it, while just 25% gave it to Obama.
One of Bill Clinton's best-known strategists, James Carville, told CNN he had been left with "one overwhelming impression ... It looked like Romney wanted to be there and President Obama didn't want to be there....It gave you the impression that this whole thing was a lot of trouble."
Romney needed a good night after being confronted with setback after setback over the last two months that have left him behind Obama in the polls. While Obama remains favourite to secure re-election on 6 November, Romney may at least have stopped his gradual campaign slump.
The first of the clashes came over the economy, with Obama asking how Romney was simultaneously going to cut the country's burgeoning defict while at the same time cutting $5 trillion in taxes for the wealthy, extending Bush era tax cuts and raising military spending, a total of $8 million.
Romney just flat-out denied it. In the tone he maintained most of the night, he said: "I think first of all, let me - let me repeat - let me repeat what I said. I'm not in favour of a $5 trillion tax cut. That's not my plan...So you may keep referring to it as a $5 trillion tax cut, but that's not my plan."
Obama, seemingly frustrated with Romney's elusiveness, retorted that it had been his plan for 18 months. "And now, five weeks before the election, he's saying that his big, bold idea is, 'Never mind."
At times, Romney patronised the president, saying that he did not understand business or accountancy. "Mr President, you're entitled to your own airplane and your own house, but not your own facts," he said at one point. In another powerful attack which is at the core of the Romney message, he listed unkept promises and told Obama: "You've been president for four years."
The president, by contrast, was hesitant in his responses. One of the biggest surprises was that he failed to deliver any of the attacks that have been successful on the campaign trail and which have been used to devastating effect in television ads in swing states. There was no mention of Romney's disparaging remarks about the 47% of the population being freeloaders, nor of his opponent's tenure at Bain Capital.
The main image of the night will be of Romney, eyes alight, gesticulating from the podium with a rarely-seen passion while Obama, playing into his image as professorial, delivered most of his answers with his head down.
Romney did not raise the killings of the US ambassador to Libya Chris Stevens and three other Americans, an emotive issue. Although the debate was meant to be devoted to domestic policy, there has been speculation he might attempt to slip it in.
On health care reform, Obama defended his controverial changes to expand coverage, saying it was almost identical to changes introduced by Romney while he was governor of Massachusetts.
Romney denied they were identical and claimed Obama's plan increased cost and reiterated he would repeal the reform.
"In my opinion, the government is not effective in bringing down the cost of almost anything. The right answer is not to have the federal government take over health care,'' Romney said.
Both candidates hit the campaign trail again on Thursday, with Obama holding rallies in Colorado and Wisconsin and Romney in Virginia. It was not a disastrous night for Obama. That calm, measured approach is part of the reason many Democrats like him and it may appeal too to independents.
Most debates have little impact on the eventual outcome but there have been exceptions, such as the 1960 one and that between Al Gore and George W. Bush in 2000. While this one will not go down as comparable game-changers, it will at least change the growing perception of Romney as a loser, even if only temporarily.
guardian.co.uk © Guardian News and Media Limited 2010