Politifact gives the award to Mitt Romney.
“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.”