DES MOINES - Republican vice presidential candidate Paul Ryan made his debut solo on the campaign trail Monday going head-to-head with President Obama in Iowa, reigniting their long-standing public policy disputes while trying to win over voters in this critical swing state.

Ryan and Obama were traveling separately and while their paths didn't cross it was clear their sights were set on each other.

Obama used his first stop of the day in the southwestern farming community of Council Bluffs to blame Ryan for helping block legislation that would have provided farmers here with financial aid.

"He's one of those leaders of Congress standing in the way," Obama told the crowd of about 4,000.

About 130 miles to the east, Ryan was returning fire, telling his own enthusiastic crowd of admirers at the Iowa State Fair that Obama's policies have hurt the middle class, killed jobs and increased poverty.

"Obama has given us four years of trillion dollar-plus deficits," Ryan said. "He's making matters worse and he is spending our children into a diminished future."

Ryan took aim at an Obama initiative that waived a work requirement for people receiving welfare, calling it "disturbing," and noting the work provision is part of the bipartisan welfare reform law passed in 1996 and signed by then-President Bill Clinton, a Democrat.

"That's a change in the wrong direction," Ryan said. "We want to give people a hand up, not hand outs."

Monday was Ryan's third day on the campaign trail after Republican presidential candidate Mitt Romney introduced the Wisconsin congressman as his running mate in Norfolk, Va., Saturday.

But it was hardly the first time Ryan exchanged rhetorical fire with Obama. The two have been trading barbs since January 2010, when Ryan first confronted the president on live television about bloated federal spending.

When Obama denounced Ryan's signature budget plan as "social Darwinism," Ryan blamed Obama for increasing the federal budget deficit and has pledged to repeal the president's signature health care reforms.

Ryan was heckled by protesters during his speech at the state fair, but he appeared unfazed by it. He said he learned to deal with such exchanges during Wisconsin's heated recall election of Republican Gov. Scott Walker.

"It's like a sport," Ryan said of the hecklers as he left the fairgrounds.

The Ryan-Obama battle raged on behind the scenes as well, with campaign aides exchanging charges when the candidates weren't.

Romney's aides disputed Obama's claim that Ryan helped block the farm bill. Ryan actually supported providing drought aid in the House, but the measure died in the Senate, they said.

Obama aides, meanwhile, called Ryan's budget plan "radical," saying it would "extend tax cuts for millionaires and billionaires while balancing the burden on the backs of the middle class."

Iowa fairgoers were mixed about Ryan.

"How can someone who has such limited work experience lead the nation?" asked Tom Gaukel, 45, a graphics designer, noting that Ryan has spent most of his career in Congress.

Jan Tetrick, 74, of Adel, Iowa, said she likes Ryan's plan to reform Medicare, but would have voted for Romney no matter who he picked as a running mate.

"It makes no difference," Tetrick said. "I just want to get the administration out that is in right now."