GREER, S.C. — Republican presidential candidate Mitt Romney said Thursday that he has never paid less than 13 percent of his income in taxes during the past decade.
But he declined anew to release the records that would prove it.
"I did go back and look at my taxes and over the past 10 years I never paid less than 13 percent. I think the most recent year is 13.6 or something like that. So I paid taxes every single year," Romney told reporters after landing in South Carolina for a fundraiser.
Romney has released his 2010 tax return and has pledged to release his 2011 return before the Nov. 6 election.
Democratic Senate Majority Leader Harry Reid, citing an anonymous source, has charged that Romney didn't want to release any more of his returns because the Republican candidate had paid no taxes in some years.
"Harry Reid's charge is totally false. I'm sure waiting for Harry to put up who it was that told him what he says they told him," Romney said.
Obama campaign spokeswoman Lis Smith responded by telling Romney to "prove it."
"He has forfeited the right to have us take him just at his word," Smith said.
Romney commented as his campaign worked to stay on the offensive in the increasingly heated debate over the future of Medicare.
"Which of these two do you think is better?" Romney asked as he stood next to a whiteboard comparing his Medicare plan with Obama's.
"This is a debate we want to have, this is a debate we need to have and this is a debate we're going to win," Romney running mate Paul Ryan said at an appearance in Ohio.
The Wisconsin congressman's addition to the GOP ticket this past weekend drew immediate scrutiny to a budget proposal he drafted that proposes to transform Medicare into a voucher-like system for future retirees.
In turn, Romney and Ryan called attention to President Barack Obama's health care law, which is funded in part by future savings from Medicare, and accused him of "raiding" the program of billions of dollars.
Meanwhile, The Philadelphia Inquirer and the Centre Daily Times reported Thursday that a new poll of Pennsylvania voters shows Obama holding a 6-point lead over Romney.
The polling was conducted by researchers at Franklin & Marshall College in Lancaster, led by professor and state political analyst G. Terry Madonna.