Obama economic adviser Austan Goolsbee did characterize Obama's stance on NAFTA as being "more about political positioning than a clear articulation of policy plans," according to a long memo written by a Canadian official that was obtained by the Associated Press.

The memo contradicts initial suggestions by the Obama campaign that no such conversation ever happened — meaning that this story has suddenly taken a turn for the worse for the Obama campaign.

But Goolsbee himself is disputing the memo's content, saying he never described Obama's stance on NAFTA as being simply rhetoric.

"That's a pretty ham-handed description of what I answered," Goolsbee said. "A: In no possible way was that a reference to NAFTA. And B: In no possible way was I inferring that he was going to introduce any policies that you should ignore and he had no intention of enacting. Those are both completely crazy."

The memo, however, suggests otherwise. "Noting anxiety among many U.S. domestic audiences about the U.S. economic outlook, Goolsbee candidly acknowledged the protectionist sentiment that has emerged, particularly in the Midwest, during the primary campaign," the memo says. "He cautioned that this messaging should not be taken out of context and should be viewed as more about political positioning than a clear articulation of policy plans."

The memo continued: "On NAFTA, Goolsbee suggested that Obama is less about fundamentally changing the agreement and more in favour of strengthening/clarifying language on labour mobility and environment and trying to establish these as more 'core' principles of the agreement."

This latest turn in the saga comes amid skirmishing between the two camps over NAFTA, a highly-charged issue in Ohio, where voters go to the polls tomorrow in what could be a contest that decides the outcome of the race.