...as in "Romney's gaffe," or "Obama's gaffe"...
Wikipedia points out that a political gaffe, generally called a Kinsley gaffe, is when the politician "reveals some truth that [he/she] didn't intend to admit."
Journalist Michael Kinsley is the one who pointed out that what we usually consider a political gaffe is actually the truth, told by politicians inadvertently. Perhaps they privately believe something but publicly can't admit it, or maybe they're just saying what's really on their mind.
In any case, these gaffes are often used gleefully by the opposing candidate or the press.
A recent infamous gaffe was committed by Rep. Todd Akin (R-MO), who claimed that in cases of "legitimate rape" a woman's body keeps the fetus from surviving, therefore making abortions in the case of rape unnecessary. In this instance, he was wrong on the facts as well as his terminology.