Mitt Romney delivered a series of tough shots at President Obama's first term during Wednesday's first presidential debate, leaving the president on his heels for much of the night and potentially gaining badly needed momentum for the final stretch of the 2012 race.

There were no knock-out punches at the forum in Denver, but Romney framed Obama as incapable of turning around the economy, accusing the president of ushering in an era of "trickle-down government" that left Americans in need of a fresh path to the future.

"Middle income families are being crushed," Romney told the president. "The question is how to get them going again. Going forward with the status quo is not going to cut it with the American people who are struggling today."

Obama countered that Romney was promising an economic fairy tale in which he would cut taxes for all Americans, increase defense spending and stanch the flow of red ink overwhelming the national budget. Obama repeatedly hammered Romney for what he said would amount to a $5 trillion tax cut, including a break for the wealthiest Americans.

"Math, common sense and our history show us that is not a recipe for growth," Obama said.

The presidential candidates exchanged blows over domestic policy during the 90-minute forum, with Romney proving the more aggressive of the pair in the opening passage of the debate.

Romney said the president was distorting the GOP tax plan, while pushing through a blueprint that would cripple small business and halt already stagnant job growth.

"I've got five boys," Romney said, seeking to add a personal flair to his economic appeal. "I'm used to people saying something that's not always true, but just keep repeating it."

The most heated exchange of the night came when Romney and Obama clashed over their respective energy plans. Obama accused Romney of protecting the interests of big oil, but the Republican challenger said the president was wasting taxpayer dollars on government investments in green energy programs.

"You don't just pick the winners and losers -- you pick the losers," Romney said pointing to the Obama administration's $535 million investment in Solyndra, a solar-panel manufacturer that ultimately went bankrupt.

The candidates exhibited strikingly different body language through the early part of the debate. Obama avoided eye contact with Romney, and appeared exasperated, and even angry as his opponent unleashed critiques on his policies. Romney, who has fought the stereotype of himself as aloof and patrician, maintained eye contact and smiled while the president spoke. The Republican seemed much more engaged.

Some Democrats were baffled that Obama appeared to leave home much of the arsenal with which the party has attacked Romney for months. There was no mention of Romney's work at Bain Capital, or his comments about the 47 percent of Americans being dependent on government.

Obama's strategy appeared to be that of a frontrunner determined to avoid confrontation or controversy. According to a slew of recent polls, Romney is trailing Obama in a handful of swing states, and entered the night with far more to prove.

After the debate, political analysts said Romney had risen to the challenge, apparently benefiting from nearly two dozen debates during a contentious Republican primary. But Democrats said nothing that happened Wednesday would change the basic dynamic of a race that has so far favored the president.