Romney didn't flinch under fire from the man who has replaced him as the GOP front-runner, saying that Perry, whose state has had the most new jobs created in the last three years, benefited from the lack of an income tax, an all-GOP legislature, and oil and natural gas riches. To take credit for those conditions would be "like Al Gore saying he invented the Internet," Romney said.
Later, the two argued over Social Security. Perry defended comments he has made that the retirement program is a "Ponzi scheme," saying that anyone who asserts young people will ever get benefits from it is telling a "monstrous lie to our kids." Social Security needs radical restructuring, he said.
Romney disagreed, saying that Social Security works for millions of Americans.
"Our nominee has to be someone who isn't committed to abolishing Social Security but who is committed to saving Social Security," Romney said. "I will be sure that we keep the program and make it financially secure."
It was the first of three televised debates scheduled over the next two weeks, signaling a more intense phase of the Republican contest, four months before the first votes will be cast in the Iowa caucuses. The field is bound to consolidate as donors and party leaders who have remained on the sidelines make their calculations of who is most electable.
Already, the collision between Perry and Romney, the two leaders in recent polls, has generated much of the energy in the race.
Economic issues dominated the debate, sponsored by NBC News and Politico. With the unemployment rate stuck at 9.1 percent, the candidates clashed one day before President Obama was scheduled to present a jobs plan during a joint session of Congress.
Perry, who has had little debate experience, seemed comfortable in his first turn on the national stage.
In three weeks since joining the campaign, Perry has become the race's latest front-runner, and all the media attention to his remarks and record has blotted out other candidates, particularly Rep. Michele Bachmann of Minnesota, who shares a similar political base.
Perry went into the debate facing great risk and great opportunity: A steady performance could only help him with donors, GOP activists, and the party establishment, but if he tripped up or looked extreme, the same crucial audiences could be scared off.
Perry's ascent has hampered Bachmann's ability to expand her support. Polls show that religious conservatives and tea party activists, demographics she needs for success in Iowa and New Hampshire, have been moving toward the Texas governor.
A slow start
The debate provided Bachmann an opportunity to get some of her momentum back, but she was virtually a spectator for the first 70 minutes. "Obamacare is killing jobs," she said at one point, repeating one of the main elements of her stump speech.
Romney, the previous front-runner, did well in the last two debates by staying above the scrum as his rivals fought one another. The rise of Perry forced him to become more aggressive Wednesday.
In recent days on the campaign trail, the former Massachusetts governor has begun courting tea party groups, and he came out with a detailed job-creation plan Tuesday to counter Obama. Romney also has contrasted himself with Perry, emphasizing his experience in private business and noting that Perry has been a professional politician since 1985, when he was sworn in to the Texas House as a Democrat.
Perry, for his part, has hit Romney on the pace of job creation in Massachusetts during his term in office, and for enacting a health-care plan that required individuals to buy insurance in that state, a feature shared with Obama's national program.
"It was a great opportunity for us as a people to see what will not work, which is an individual mandate," Perry said.
Texas Rep. Ron Paul, a libertarian who outpolls many of the contenders and who finished second to Bachmann in last month's straw poll in Ames, Iowa, sought to inject himself into the conversation. His campaign ran a TV ad attacking Perry, a former Democrat, for having supported Gore for president in 1988.
Paul said that Perry is "less conservative than meets the eye."
Former Utah Gov. Jon Huntsman cast himself as a voice of reason, refusing to join the other candidates in taking interest-group pledges, and defending his comments that the GOP was gaining an image as the "antiscience" party because of some candidates' skepticism about global climate change and evolution.
"When you make comments that fly in the face of what 98 out of 100 climate scientists have said, when you call to question evolution, all I'm saying is that in order for the Republican Party to win, we can't run from science," Huntsman said. Such positions "turn off" voters, he added.
Ex-House Speaker Newt Gingrich, former Pennsylvania Sen. Rick Santorum, and Georgia businessman Herman Cain all fought for space on the radar screen.
Santorum, who led the fight for welfare-to-work legislation in the 1990s, said that "no one in the United States Senate has done more" for poor people. He said that "ending the culture of dependency" was the right thing to do, "not to save money, but to save lives."
On Monday, the Republican hopefuls will do it all over again, in Tampa, Fla., the site of next year's Republican National Convention, and then debate for a third time this month on Sept. 22 in Orlando, Fla.
Contact politics writer Thomas Fitzgerald at 215-854-2718 or tfitzgerald@phillynews, or on Twitter @tomfitzgerald. Read his blog, "The Big Tent," at www.philly.com/BigTent.