The effects of the trade pact are still hotly debated, but studies indicate the deal has resulted in record exports from Texas to Canada and Mexico. But a lot of blue-collar workers believe it has cost jobs.
McCain says that trade and national security are "interconnected with each other."
Both Democratic candidates said at a debate this week that they would insist on renegotiating NAFTA and would threaten to opt out of the agreement unless Canada and Mexico come to the negotiating table.