Ryan's address has come under scrutiny by numerous fact-checking organizations.
"What they are trying to suggest is that I said Barack Obama was responsible for the [General Motors Co.] plant shut down in Janesville [Wis.]," Ryan said on NBC's "Today" show. "That is not what I was saying. Read the speech. What I was saying is the president ought to be held to account for his broken promises," Ryan said in a reference to a closed GM assembly plant in his hometown.
In his Republican National Convention speech in Tampa, Fla., Ryan pointed out then-candidate Obama's visit to the plant in October 2008 but did not mention GM had already announced in July the plant would be shuttered and had done so by December before Obama arrived took office in January 2009.
Ryan defended a reference in his speech to Obama's failure to accept recommendations in a report from a bipartisan debt commission. Ryan's speech did not mention that he was a member of the commission and ultimately voted against the final plan.
The report lacked ideas for dealing with "runaway healthcare entitlement spending," Ryan told NBC.
During a campaign stop Tuesday in Westlake, Ohio, a suburb of Cleveland, Ryan said Obama compared unfavorably with former President Jimmy Carter, the Los Angeles Times reported.
Ryan said unemployment, bankruptcies and delinquent mortgages are worse than they were when Carter lost his re-election bid to Ronald Reagan in 1980.
"When it comes to jobs, President Obama makes the Jimmy Carter years look like good old days," Ryan said. "If we fired Jimmy Carter then, why would we rehire Barack Obama now?"
Hecklers interrupted Ryan when he blamed Obama for Standard & Poor's downgrade of the U.S. credit rating in August 2011.
"People can shout, people can use words, but people cannot escape the facts," he said.
Obama campaign spokesman Danny Kanner said in a statement Ryan voted for George W. Bush administration spending that increased the federal deficit.
"While Romney and Ryan may want to revise the past," Kanner said, "they can't make up their own facts."
Standard & Poor's said at the time the decision to downgrade was based on its belief that a debt-reduction plan agreed to by the White House and Congress "falls short of the amount that we believe is necessary to stabilize the general government debt burden by the middle of the decade." The credit-rating agency blamed "political brinksmanship" and said the statutory ceiling on federal borrowing "and the threat of default have become political bargaining chips in the debate over fiscal policy."