MOORESVILLE, N.C. — Republican Mitt Romney’s presidential campaign took on a buoyant tone on Sunday, as Romney and his new vice presidential running mate, Paul Ryan, basked in the support of cheering crowds in North Carolina.

The rallies, starting with one at a NASCAR training center, showed how Romney’s selection of the Wisconsin congressman as his running mate has injected new energy into a campaign that had struggled to move beyond Democrats’ efforts to cast Romney as a wealthy former private equity executive who cannot relate to middle-class Americans.

“Are we going to win North Carolina?” Ryan told a boisterous crowd in Mooresville.

“Yeah!” the crowd shouted back.

“We can either stay on the current path we are on,” Ryan said. “A nation in debt, a nation in despair, a nation of unemployment. ... Or we can change this thing and get this country back on the right track.”

Hours earlier in Virginia, where Romney had introduced him as the No. 2 on the Republican ticket on Saturday, Ryan, 42, the chairman of the U.S. House of Representatives Budget Committee, told reporters that being thrust into the presidential campaign was “very exciting.”

“We’re going to win this campaign,” he said. “We’ve got the wind behind us.”

Romney, 65, seemed happy to have a sidekick to end what he has called the “two against one” dynamic of the race, with President Barack Obama and Vice President Joe Biden on one side and Romney on the other.

“It’s a far more compelling dynamic than just being out there on my own,” Romney said late Saturday.

President Barack Obama on Sunday dubbed Paul Ryan as the “ideological leader” of congressional Republicans.

“Just yesterday, my opponent chose his running mate, the ideological leader of Republicans in Congress, Mr Paul Ryan. I want to congratulate Mr Ryan. I know him, I welcome him to the race,” Obama said at a fundraiser in Chicago, speaking over boos from some in the audience at the mention of Ryan’s name.

“He’s a decent man. He is a family man. He is an articulate spokesman for Governor Romney’s vision. But it’s a vision that I fundamentally disagree with,” he said.

The remarks were Obama’s first comments about Republican challenger Romney’s selection of the Wisconsin congressman as his running mate.

On Sunday, Republican National Committee Chairman Reince Priebus cast Romney’s campaign as the one being honest with Americans about the nation’s fiscal future and said Obama’s team is more interested in attacking Romney.

Selecting Ryan shows that Romney “has the leadership and courage to present to the American people a real contrast and a real debate that the American people deserve,” Priebus said on NBC’s “Meet the Press.”

Even so, Romney’s campaign team continued to stress that Romney would propose his own fiscal plan, suggesting that it did not want the former Massachusetts governor to be tied to everything in Ryan’s budget plan.

Ryan’s plan calls for an end to the guaranteed benefit in Medicare and replaces it with a system that would give vouchers to recipients to pay for health insurance.

On Sunday, Romney campaign officials declined to comment about the vice presidential vetting process and how many years of tax returns were required, saying it was meant to be “private and confidential.” It was unclear if Ryan’s tax returns, which were stored in a safe in a locked room at Romney’s campaign headquarters, will be released to the public. Tim Pawlenty, the former Minnesota governor who was a potential Romney running mate, told George Stephanopoulos, the host of ABC’s “This Week,” Sunday that he also had to submit several years of tax returns during the search for a Republican vice presidential candidate.