AKRON, Ohio — What a difference two weeks — and a lackluster debate performance by President Barack Obama — has made for Republican presidential candidate Mitt Romney in key swing states.

Mired in dismal poll numbers in Ohio two weeks ago, a confident and resurgent Romney returned to the Buckeye State and stumped in rural Iowa on Tuesday as new polls show him gaining fast in battleground states and nationally. In one key measure, he marked his first edge over Obama nationally.

“I’ll do everything in my power to strengthen once again the American farm,” a buoyant Romney vowed at an event in Van Meter, Iowa, where he outlined his agriculture policy. “I’ll do everything in my power to strengthen our economy, to create good jobs and rising incomes. I’ll strengthen the values of our homes and communities.”

Obama, working to hold his narrowing lead in Ohio, held a rally at Ohio State University in Columbus and used the final day of voter registration in the state to implore supporters to sign up and cast their ballots on Nov. 6.

“Everything we fought for in 2008 is on the line in 2012,” Obama told an estimated crowd of 15,000. “The American people have worked too hard, and the last thing we can afford to do right now is to go back to the very same policies that got us into this mess in the first place. I cannot allow that to happen. I will not allow it to happen.”

A CNN/ORC International poll of Ohio released Tuesday found Obama ahead 51 percent to 47 percent, a 4-point lead instead of the 7- to 10-point lead he enjoyed before the debate.

“Polls will go up and down, but most of them taken together tell us the campaign is close and will continue to be close nationally and in these key battleground states,” said Romney senior adviser Kevin Madden. “Part of our focus as a campaign is on finding these voters who still haven’t made up their mind, along with voters who voted for Obama in 2008 but are disappointed in the state of the economy, and persuading them to vote for Governor Romney.”