We're often asked how fact-checking sites can be biased, since they purportedly only report facts.

This chart demonstrates what we mean. Please send this to anybody you know who still thinks that left-leaning fact-checking sites should be trusted.

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We assembled this chart by sorting PolitiFact's complete list of "Pants On Fire" rulings. We filtered out any rulings of chain email or anonymous Facebook posts (although these were virtually all conservative viewpoints), as well as politicians or organizations who had only one "Pants On Fire" ruling (but again, even these were mostly conservatives).

The results are, sadly, not surprising. But the situation is grave. PolitiFact (and other supposedly unbiased fact-checking sites) paint Mitt Romney as a serial liar. They also unfairly tarnish Michele Bachmann as a liar, when anybody who follows her already understands that many of her statements aren't meant to be truthful in the first place -- she simply says what she feels.

Notice that PolitiFact states that Barack Obama lies more than Sarah Palin. That's good news -- but keep in mind that Barack Obama's statements are across two campaigns, while Sarah Palin's were across only one.

To have any semblance of fairness, PolitiFact should play it 50/50 and present an equal number of lies from both sides. They clearly are not concerned with any pretense.