Barack Obama says that the next president must develop a new approach to foreign relations. And so he has promised to invent one based on "aggressive personal diplomacy" with Iran and possible meetings with the despotic rulers of Cuba and Syria.

Perhaps some good would come from this. I really have no idea. Before ordering Air Force One to Tehran, however, Obama may want to consider some aggressive personal diplomacy with Canada. In the wake of the Democratic primaries, we’ll probably need to patch up relations with our neighbor to the north.

That’s because for the last few weeks, it’s been hard to tell whether Obama and Hillary Rodham Clinton have participated in their partyÕs presidential nominating process or a NAFTA-bashing contest. Unfortunately, both candidates have threatened to pull out of this vital economic agreement.

"I will make sure that we renegotiate," says Obama. "I think we should use the hammer of a potential opt-out as leverage to ensure that we actually get labor and environmental standards that are enforced."

Clinton, whose husband pushed for NAFTA as president, speaks the same language: "I will say we will opt out of NAFTA unless we renegotiate it, and we renegotiate on terms that are favorable to all of America."

This reckless rhetoric doesn’t thrill Canadians or Mexicans. They thought that NAFTA was a well-established set of rules for conducting business on our shared continent. It allows people to exchange goods and services without interference from tariffs whose main purpose is to restrict consumer choice and protect special interests.

For the last few weeks, however, NAFTA has been a political punching bag. As Clinton and Obama have chased votes in Ohio, they’ve taken swing after swing at this important agreement–even though half of the Buckeye StateÕs exports are sold to Canada and Mexico.

There’s always the hope that these politicians don’t quite mean what they say. The Obama campaign recently found itself embroiled in a controversy over its true intentions with respect to NAFTA. On February 8, Obama’s top economics advisor, Austan Goolsbee, met with officials at the Canadian consulate in Chicago. In a memo obtained by the Associated Press, a Canadian staffer described the encounter: "Goolsbee candidly acknowledged the protectionist sentiment that has emerged, particularly in the Midwest, during the primary campaign."

As the memo continues, the shoe drops: "[Goolsbee] 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."

So maybe Obama isn’t really against NAFTA after all.

In some ways, this is hopeful. If Obama becomes our next president, it suggests that he won’t be as hostile to global trade as his public remarks have indicated. Less encouraging is what it tells us about his willingness to pander to voters who are feeling economic anxiety.

Clinton isn’t much better. She used to speak favorably about trade. Now she isn’t merely advocating a "time out" on new trade deals, as she did earlier in her campaign, but a possible roll back of existing ones.

If the United States were to quit NAFTA, our whole economy would suffer. Even if all we wanted to do was renegotiate NAFTA, it would be the height of arrogance to think that only the U.S. gets to make changes. Mexico and Canada would have their own "change" priorities too. And agriculture would likely feel the brunt of it. Our livelihoods depend upon export sales and none of us would welcome pre-NAFTA tariffs in two of our biggest markets.

When it comes to international trade, I wish more Democrats would listen more to one of their own: Robert Reich, who was the labor secretary in the Clinton administration. "It’s a shame the Democratic candidates for president feel they have to make trade–specifically NAFTA–the enemy of blue-collar workers, he wrote on his blog recently. "NAFTA is not to blame."

The irony is that free trade can flourish under a Democratic president. Just as it took a Republican like Richard Nixon to go to, and open, China, it took a Democrat like Bill Clinton to wrap up NAFTA.

President Clinton chose to lead his party in a promising new direction, rather than submit to old-fashioned populist impulses. The two candidates who are striving to take up his mantle would do well to learn from his lesson.

Dean Kleckner, an Iowa farmer, chairs Truth About Trade & Technology