SUN LAKES, AZ -- In what was a free-wheeling town hall that felt more like a rally, Mitt Romney, with shirt sleeves rolled up and pacing the stage, seemed to be able to do no wrong -- receiving generous applause, even as he praised one of the most controversial political figures in recent American history: former Vice President Dick Cheney.

"I think it was last weekend I was watching C-SPAN, and I saw Vice President Dick Cheney and he was being asked questions about a whole host of issues -- following 9/11, the affairs in various countries in the world. And I listened to him speak and said whether you agree or disagree with him, this a man of wisdom and judgment, and he could have been president of the United States," Romney told the crowd to their loud approval. "That's the kind of person I'd like to have -- a person of wisdom and judgment."

That answer came to a question about whether Romney would name a "Tea Party person" as his vice presidential nominee. Romney demurred, saying only that his one "overwhelming criteria" for a VP choice, should he be lucky enough to make one, would be that that person is ready to become president, as he felt Cheney was.

Romney, fresh from a fundraising luncheon, was buoyed by a crowd estimated to be nearly 800 strong -- mostly seniors, whose parked cars stretched for block after manicured block here in the Sun Lakes golf and retirement community near Phoenix. It was perhaps the largest, friendliest Romney crowd of the campaign season, which one Romney aide said showed the candidate's strength in Arizona, but also could have been related to a front-page story in this morning's Arizona Republic, which several attendees said was how they learned of the event.

The former governor of Massachusetts stung his biggest rival, Rick Perry of Texas, on issues likely to carry more than a little water in this now early-voting, senior-heavy, border state: Social Security and immigration.

On Social Security, Romney joked, "You may have watched the debate. It came out in a big way."

"Social Security is not a Ponzi scheme," Romney began telling a questioner, to the laughter and approval approval of the crowd. "Social Security has worked for 75 years pretty darn well. You guys have not taken advantage of Social Security; you contributed to it. It's a savings plan, a pension plan. There are no bad guys in Social Security, so I don't call it a Ponzi scheme."

But Romney, who said he wouldn't touch the plan for current seniors, admitted the funding system would need changes in the long term to keep it solvent for younger generations. How would he accomplish this?

"No.1, we're not going to change it by sending it back to the states. Gov. Perry, in his book, said: 'Look, it's unconstitutional at the federal level, give it back to the states,'" he said. "Look, you can't have people who move from state to state to state having different plans state to state. I wouldn't want the state legislatures raiding the trust funds of Social Security state by state. It needs to be a federal entitlement. I will save Social Security as a federal program and as a federal entitlement."

On immigration, Romney gave mostly his standard answer, and did not reference Perry directly -- instead, the crowd did it for him. Romney said that he likes legal immigration, that he supports building a fence to stop illegal immigration, and that he wants to turn off the "magnet" in the United States.

"We create advantages for people to come here illegally -- jobs, employers who hire people who are here illegally, giving in-state tuition to people who come here illegally," Romney said, drawing laughs and applause just as he mentioned in-state tuition, something Perry has approved in Texas, of which Romney has at times been sharply critical.

Romney took some criticism of his own in one testy exchange. He was questioned about his Massachusetts health-care plan, which one woman in the crowd pressed him to admit was a failure. The questioner continued speaking over Romney as he first tried to respond, saying he put "Obamacare" into place in Massachusetts, and that he made Masschusetts the most expensive state for health care.

"First of all, you're wrong," Romney responded, showing perhaps a flash of annoyance. "And let me explain why I said that. First, you said Obamacare. We had ours in place before Obamacare. We had ours in place before Obama had his. Four years before, we put our bill in place. And let me tell you -- Massachusetts health-care is the most expensive in the nation -- and it was before our bill -- and it was after."

That exchange aside, the crowd was consistently a friendly one, which after also covering Iran, school choice, and a few other meaty issues, presented the following as the penultimate question: Everyone who becomes president turns old on the job. Can you tell us why do you want to take on the responsibility?

Romney laughed as he responded. "It won't happen to me! It won't happen to me! I'm already old! I'm 64," he said to applause, adding: "I could live here!"

As he put up his microphone, Romney was mobbed -- as if he were Justin Bieber and the crowd, preteen girls. Autograph seekers with Romney's jobs book in hand, and seniors with iPhones looking for pictures surged around him, as he made his way towards the exits and a final evening fundraiser.

As he approached the door, Romney shook hands with one supporter who pumped his arm vigorously as he told the candidate, "I named my yacht 'Deregulation'. It was a political statement."