A key labor surrogate for Hillary, International Association of Machinists president Tom Buffenbarger, has now opened fire on Obama over the Canadian TV report suggesting that a senior Obama official privately assured a Canadian official that Obama's anti-NAFTA stump talk was just "campaign rhetoric."

From an IAM press release...

"I am appalled but not surprised by this report," said IAM International President Tom Buffenbarger. "Working families cannot trust a candidate who telegraphs his real position to a foreign government and then dissembles in a nationally televised debate."

The Obama campaign has released a statement that didn't address whether the conversation had happened but did say that the report inaccurately represented Obama's position on NAFTA. NAFTA is a highly-charged issue in Ohio. So a report like this -- and efforts like this one by Buffenbarger to keep the story going -- could conceivably have an impact on the primary, which is only days away.

Separately, it's worth keeping in mind that Buffenbarger apparently has little difficulty speaking his mind when it comes to Obama. He recently denounced Obama supporters as "latte-drinking, Prius- driving, Birkenstock-wearing, trust fund babies" and said that Obama wouldn't "last a round against the Republican attack machine."

Late Update: A Canadian embassy official flatly denies to ABC News that the conversation ever took place: "It didn't happen."