Clinton has said on the campaign trail that she opposes the Trans-Pacific Partnership, a 12-nation trade deal negotiated by President Barack Obama's administration, citing its lack of provisions to crack down on currency manipulation.
But McAuliffe said in an interview with Politico that he believes she'd flip-flop and support the deal.
"I worry that if we don't do TPP, at some point China's going to break the rules -- but Hillary understands this," he said. "Once the election's over, and we sit down on trade, people understand a couple things we want to fix on it, but going forward, we got to build a global economy."
Pressed on whether Clinton would reverse her position, McAuliffe told Politico: "Yes. Listen, she was in support of it. There were specific things in it she wanted fixed."
Already, Republican nominee Donald Trump is seizing on McAuliffe's remarks as evidence Clinton is willing to flip-flop.
"Just like I have warned from the beginning, Crooked Hillary Clinton will betray you on the TPP," Trump tweeted.