MESA, Ariz. - As two new polls put former Sen. Rick Santorum at the head of the pack in the GOP primary race, Mitt Romney leaped onto a stage in the battleground state of Arizona tonight to continue his defense of his conservative credentials while warning voters of politicians who may have been "infected by the Washington disease."

"My conservatism did not come so much from reading the writings of great conservative scholars as it did from living my life, my family my faith, my business," said Romney, speaking to thousands in an outside amphitheater in Mesa.

"Conservative values were also part of my business experience, because in business you don't have a choice about balancing your budget, you either balance your budget or you go bankrupt," said Romney. "So I learned time and again the principles of conservatism."

A new daily tracking poll conducted by Gallup shows Romney and Santorum in a statistical dead heat, with Romney leading at 32 percent and Santorum with 30 percent of likely Republican registered voters. Santorum is also favored among conservative voters, a fact Romney seemed to swat at as he brought up social issues, a subject that was nearly void from his stump speech before last week.

But over this past week, which included a win by Romney in the Conservative Political Action Conference's straw poll, Romney has paid more attention to highlighting his conservative principles.

And tonight he continued to do just that, providing a laundry list of events in his life where he says he's had to flex his "conservative values."

"There are also some social issues that came up that were significant during my term in office," said Romney, who before last week rarely discussed social issues on the stump. "You may recall that our Supreme Court said that, that John Adams had written into our Constitution a protection for same sex marriage. Adams [would] be surprised."

"And I led the fight to get an amendment to our Constitution to reverse that ruling, we missed by one vote," he said. "But we went to make sure that we didn't have our same sex marriage go throughout the country and we were able to enforce a - I think it was a 1913 - law that kept Massachusetts from becoming the Las Vegas of same sex marriage."

Romney continued to assail his opponents as Washington insiders, though he strayed from direct, forceful attacks on the three other candidates, instead pointing out the differences in their backgrounds.

"And the challenge that we have in Washington is that people go there and they get infected by this Washington disease, which makes them think that government is a source of our greatness, that government should guide our lives and they become more and more insistent on intruding government into our lives," said Romney. "And I'm absolutely convinced that we finally have to have people who go to Washington who believe in people and believe this should be a nation of, by, and for the people, and of, by, and for the government."

"We've got four guys on the Republican side, all running for president," said Romney, as chants of "Mitt! Mitt! Mitt!" emerged from the crowd. "My guess is this crowd is kind of partial to me, is that right?"

"And there are some differences. I'm sure there are some issues here and there where we can point out distinctions. But perhaps the greatest distinction is what we've done during our lives, our life experiences," said Romney.

"Congressman Paul was a doctor, then went into government, but the other guys have spent their life entirely in government, and in my view it's helpful to have been involved in two businesses, an Olympics and a state, and to run all- and to have a chance to run those as an executive."

"We elected a president, we elected in President Obama someone who had never run anything. Who had never been a leader. We're not going to do that in the Republican party. Let's not nominate someone who hasn't done anything and has not been a leader," he said.