Looking to claw his way back into a race that has seen Obama hold an edge among voters, Romney was on the offensive throughout the 90-minute encounter with the incumbent Democrat as he sought to put his campaign back on a sound footing with under five weeks to go until the 6 November election.
Standing side-by-side for the first time after months of brutal campaign exchanges, the two men clashed over taxes, healthcare and the role of government in ways that reflected the deep ideological divide in Washington.
Appearing poised and well-prepared, Romney zeroed in on weak economic growth and 8.1% unemployment that have left Obama vulnerable in his effort to win a second four-year term. Government has taken on too big a role under Obama, dampening job creation, Romney argued.
"Now, I'm concerned that we're on the path that's just been unsuccessful. The president has a view very similar to the one he had when he ran for office four years ago, that spending more, taxing more, regulating more, if you will, trickle-down government would work. That's not the right answer for America," Romney said.
A CNN/ORC snap poll said 67% of registered voters surveyed thought Romney won the debate at the University of Denver, compared with 25% for Obama.
Mysteriously, Obama failed to mention issues his campaign has used in attack ads to damage Romney in the polls such as the Republican's now infamous "47%" video, his business record at Bain Capital and previous hard line on immigration.
Recently, Romney was damaged by a hidden-camera videotape in which he said 47% of voters were dependent on government and unlikely to support him.
The debate saw no haymaker punches thrown and not much in the way of memorable one-line zingers. Instead, it was a war of attrition as each man used facts and figures to make his points and stress the differences between them.
Romney, however, did himself some favours with crisper answers than Obama, who sounded professorial and a bit long-winded despite his staff's best efforts to get him to give snappier comments.
The White House incumbent did put Romney on the defensive about his proposals for overhauling the US tax system with a 20% across-the-board tax cut. Obama said it would cost $5 trillion (€3.87 trillion) and that it would be impossible to make up this amount by eliminating tax loopholes as the Republican talks about.
"The fact is that if you are lowering the rates the way you described, Governor, then it is not possible to come up with enough deductions and loopholes that only affect high-income individuals to avoid either raising the deficit or burdening the middle class. It's - it's math. It's arithmetic," Obama said.
Romney replied, "Virtually everything he said about my tax plan is inaccurate."
Obama also reminded Americans that Romney was proposing more of the same kind of tax cuts that Obama's Republican predecessor, former President George W. Bush, pushed through Congress in 2001 and 2003. Most Americans are willing to concede that Obama inherited an economic mess, but also believe it is his responsibility to bring back the economy.
"We ended up moving from surpluses to deficits and it all culminated with the worst recession since the Great Depression," said Obama.
In the face of attacks from Romney that the Obama healthcare overhaul of 2010 will hurt small-business hiring, Obama basically said his healthcare plan was modeled after the programme Romney put in place as governor of Massachusetts, and it "hasn't destroyed jobs" there.
After arguing for months that the Wall Street regulation legislation known as "Dodd-Frank" should be repealed, Romney was forced to concede under pressure from Obama that he would keep some financial regulations established under the law.