"Michael Dukakis created jobs three times faster than you did, Mitt," said Texas Gov. Perry, referring to the former Massachusetts Democratic governor who lost the 1988 presidential election.
"Well, as a matter of fact," replied Romney, also a former Massachusetts governor, "George Bush and his predecessor created jobs at a faster rate than you did, Governor."
The invited audience of Republicans at the Ronald Reagan Presidential Library in Simi Valley, Calif., near Los Angeles, burst into laughter on Romney's comeback. Perry succeeded Bush as governor in 2000.
In another jobs exchange, Perry said, "We created more jobs in the last three months in Texas than he created in four years in Massachusetts."
Romney noted Texas has no state income tax, a Republican legislature and state supreme court, and "a lot of oil and gas in the ground." So for Perry to claim credit for Texas' good fortune "would be like Al Gore saying he invented the Internet," Romney said.
Gore, who ran for president against Bush in 2000, told CNN in 1999 he "took the initiative in creating the Internet," which was later misquoted and distorted, becoming a devastating setback to him.
Perry said Romney's healthcare reform plan for Massachusetts -- a precursor to the federal plan signed into law by U.S. President Barack Obama last year -- "was a great opportunity for us as a people to see what will not work."
Romney defended the Massachusetts healthcare law, which mandates nearly every state resident have a minimum level of health insurance and provides free health coverage for residents near the poverty level or below. Romney said his plan was intended for his state only and said that if elected, he would move to repeal the Obama administration's law as soon as he takes office.
Rep. Michele Bachmann of Minnesota, who slipped to third place in most national polls after Perry joined the race, told Romney and Perry no president would able to overturn the law with an executive order, as both have promised.
She repeated her assertion she was the first in Congress to call for a repeal of the Affordable Care Act.
Bachmann, along with Rep. Ron Paul of Texas, former Sen. Rick Santorum of Pennsylvania, former Utah Gov. Jon Huntsman Jr., former Godfather's Pizza magnate Herman Cain and former House Speaker Newt Gingrich were asked far fewer questions than Romney and Perry.
Huntsman, who stepped down as the Obama administration's ambassador to China, said Utah under his stewardship led all states in creating new jobs.
He assailed Romney's hard-line position toward China.
"Mitt, now is not the time, in a recession, to enter a trade war," Huntsman said.
Perry labeled Social Security a "Ponzi scheme'' and said it was "a monstrous lie" to tell young workers the Social Security taxes they pay will come back to them in retirement benefits.
Romney said Perry's negative position on Social Security could disqualify him as the GOP nominee.
"Our nominee has to be someone who isn't committed to abolishing Social Security but who is committed to saving Social Security," Romney said. "Under no circumstances would I ever say by any measure it's a failure."
Perry questioned scientists' assertions that climate change is caused at least in part by human activity.
Huntsman responded that 98 percent of scientists saw a human role in climate change and "for the Republican Party to win, we can't run from science, we can't run from mainstream society."
Gingrich called Federal Reserve Chairman Ben Bernanke "the most inflationary, dangerous and power-centered chairman in the history of the Fed,'' although inflation is currently relatively low.
Paul, a Libertarian icon, suggested cutting off funds for air-conditioning in Iraq to force U.S. troops there to come home. He also stood by his calls to abolish the Federal Emergency Management Agency.