Mitt Romney insisted his campaign is not in need of a "turnaround" in spite of polls showing President Barack Obama expanding his lead in battleground states.

In an interview with CBS's "60 Minutes," the Republican presidential nominee rejected criticism from conservative pundits who have called his campaign incompetent.

"It doesn't need a turnaround," Romney insisted, pointing to national polls that have him "tied" with Obama. "I've got a very effective campaign. It's doing a very good job."

Asked about GOP worries over a hidden video that caught him dismissing Obama supporters—which he estimated to be 47 percent of the country—as having a victim mentality and being too dependent on the government, Romney said he was responsible for those comments, not his campaign.

"That's not the campaign," Romney said. "That was me, right?"

Asked about criticism that he's changed his positions on issues like abortion and gay marriage for political reasons, Romney insisted he's still following "the principals I've had from the beginning of my political life."

"But have I learned? Have I found that some things I thought would be effective turned out not to be effective? Absolutely," Romney said. "If you don't learn from experience, you don't learn from your mistakes, why, you know, you ought to be fired."

The former Massachusetts governor also defended his campaign from criticism that he hasn't been specific enough about what policies he would implement as president. Among other things, he talked about how he would handle Social Security, telling CBS's Scott Pelley that he would implement a means testing for future retirees, which would allow lower income Americans to receive more benefits than those with higher incomes.

"Higher income people won't get as much as lower income people," Romney told CBS. "By virtue of doing that, you're able to save these programs on a permanent basis."

And contrary to Obama's claims, Romney insisted he would not lower taxes for high income Americans, but rather would focus on lowering taxes for the middle class.

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"There should be no tax reduction for high-income people," Romney said. "What I would like to do is to get a tax reduction for middle-income families by eliminating the tax for middle-income families on interest, dividends and capital gains."

Pelley asked Romney what "big idea" he would pursue as president, pointing to agendas like putting a man on the Moon and the creation of Social Security. Romney pivoted back to a line from his stump speech, insisting his big idea would be to "restore" freedom.

"I want to restore the kind of freedom that has always driven America's economy. And that's allowed us to be the shining city on the hill. The kind of freedom that has brought people here from all over the world," Romney replied. "I want people to come here, legally, to want to be here. I want the best and brightest to say America's the place of opportunity, because of the freedom there to pursue your dreams. So my message is restore the kind of freedom that allows America to lead the world."