Mitt Romney, the 2012 Republican presidential nominee, gave an emotional thank you as he struck a positive tone for his party Friday in his first public speech since losing the election to President Barack Obama.

Romney told those attending the Conservative Political Action Conference near Washington that they shouldn't be pessimistic amid talk of the party's demographic challenges.

"We've lost races before, in the past, but those setbacks prepared us for larger victories," he said. "It's up to us to make sure that we learn from our mistakes -- and my mistakes -- and that we take advantage of that learning to make sure that we take back the nation."

Romney's speech was warmly received by those at CPAC, a gathering sponsored by the Washington-based American Conservative Union, which advocates for less government spending. He received several standing ovations.

"We have not lost our way," Romney said. "Our nation is full of aspirations and hungry for new solutions." Romney, a former Massachusetts governor, pointed to Republicans currently holding governorships, including some who weren't invited to the event such as New Jersey's Chris Christie, as being models for the party as it moves forward.

"I would urge us all to learn lessons that come from some of our greatest success stories, and that's 30 Republican governors across the country," Romney said. "These governors have shown that they're able to reach across the aisle, offer innovative solutions and that they are willing to take the heat."

Christie and several other Republican governors were excluded from the conference after they announced they'd seek federal money under Obama's health care law to expand Medicaid, an insurance program for the poor.

Romney seemed to make clear that he had no intention of running again for president.

"I'm sorry I won't be your president," he said. "But I will be your co-worker and I'll work shoulder-to-shoulder alongside of you."

In an earlier address, Rep. Paul Ryan, Romney's vice presidential running mate, didn't mention the 2012 race.

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Ryan, chairman of the House Budget Committee, painted a bleak picture of the economy and the federal government's financial standing. "The president says we are in a recovery," the Wisconsin lawmaker said. "I say we are in critical care."