Republican presidential nominee Mitt Romney says the upcoming debates will be tough because President Barack Obama has a tendency to "say things that aren't true."

"I think he's going to say a lot of things that aren't accurate," Romney told ABC's George Stephanopoulos in an interview that aired on Friday. "I'm tempted to go back to that wonderful line by Ronald Reagan -- 'There you go again' -- but you can't use something that's [already been used]."

"Bill Clinton used that about you the other day during the Democratic Convention," Stephanopoulos noted.

"I didn't happen to see that, but doubt we're going to pull out something from Ronald Reagan, he's one of a kind," the former Massachusetts governor explained. "But the challenge I'll have is that the president tends to, how shall I say it, say things that aren't true in attacking his opponents."

"I've looked at prior debates and in that kind of case, it's difficult to say, well, am I going to spend my time correcting things that aren't quite accurate or am I going spend my time talking about the things I want to talk about? And that's the challenge."

But President Obama may also have his hands full when it comes to fact checking the Republican nominee.

MSNBC's Steve Benen spent months chronicling Romney's "mendacity" and claimed to have found 533 falsehoods in 30 weeks, according to a tally by blogger Fred Clark.

"I don't know the Republican candidate personally, but from a distance, it appears there's a part of his brain that allows him to create some kind of deliberate blind-spot," Benen wrote during the 30th week. "It's actually a little scary to think of a leader -- a man who'd be given enormous power and influence, literally making life and death decisions on a regular basis -- who can convince himself that his falsehoods are true, and that others' truths are falsehoods."

Watch this video from ABC's Good Morning America, broadcast Sept. 14, 2012.

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(h/t: Mediaite)