That NAFTA thing? It wasn't Obama reassuring the Canadians that he was full of shit on his NAFTA attacks.
It was Hillary.
Well, ok, that's not quite true. The original assurance that it was all nonsense was, apparently, from a Hillary staffer. Supposedly the later memo that more explicitly discussed it was one of Obama's people, but the Obama campaign is challenging the wording.
(It's all in the G&M)
So Hillary was bashing the hell out of Obama for something that she was either doing instead or doing as well.
(Edit: that said, there's been a lot about how Obama's surrounded by economists. It would make sense that Obama's advisors would be almost reflexively pro-free trade even when it makes no political sense to do so and the empirical evidence is lacking. Trying to wean your typical economist from dogmatic support of international trade is difficult at best; Obama isn't the type of person to try to do it in the first place.
(Hillary was obviously unserious in attacking NAFTA, she's not going to tear down her husband's legacy, but people expect her to be talking out of the side of her mouth. It's practically a selling point to her campaign. Obama's rep is, I suppose, a double-edged sword.)
In any case, don't buy into anti-NAFTA hype unless you have a damned good reason to do so. After all, it's in Obama's book: the higher up the ladder you go, the more you interact with the people who benefit from trade, and the less you interact with people that are devestated by it. And at this point, you don't get any higher up the ladder than Clinton, Obama, and all the economists they're surrounded with.