Politifact has deemed the following the lie of the year:
It was a lie told in the critical state of Ohio in the final days of a close campaign — that Jeep was moving its U.S. production to China. It originated with a conservative blogger, who twisted an accurate news story into a falsehood. Then it picked up steam when the Drudge Report ran with it. Even though Jeep’s parent company gave a quick and clear denial, Mitt Romney repeated it and his campaign turned it into a TV ad.
And they stood by the claim, even as the media and the public expressed collective outrage against something so obviously false.
People often say that politicians don’t pay a price for deception, but this time was different: A flood of negative press coverage rained down on the Romney campaign, and he failed to turn the tide in Ohio, the most important state in the presidential election.
PolitiFact has selected Romney’s claim that Barack Obama “sold Chrysler to Italians who are going to build Jeeps in China” at the cost of American jobs as the 2012 Lie of the Year.
Virtually everything he said was a lie, so I am not sure how you choose one over the other.