WASHINGTON—Is the North American Free Trade Agreement (NAFTA) dying? Both Hillary Clinton and Barack Obama have made campaign promises to “renegotiate” the 14-year-old trade agreement that generally has resulted in a boom for U.S. trucking and railroad interests.

Since NAFTA was adopted in 1994 under the first Clinton administration, it basically created open trade, free of duties and tariffs, among the U.S. Mexico and Canada. But both Democratic candidates have sounded a protectionist tone during their campaign, threatening to renegotiate NAFTA and other free trade agreements to make them more favorable on labor and environmental grounds.

It’s hard to tell whether this is merely campaign rhetoric or an actual threat to NAFTA existence. One thing is for sure: Any talk of renegotiating NAFTA makes truckers nervous.

“Since 1993, when [President] Clinton signed the agreement, we’ve been in favor of NAFTA and free trade acts in general and that hasn’t changed,” said American Trucking Associations (ATA) President and CEO Bill Graves. “Free trade is generally good for the American consumer and we support that.”

It’s also been good for the U.S. trucking industry. Some companies, such as Indianapolis-based Celadon and Con-way’s CFI unit, garner more than 40 percent of their revenue from the lucrative north-south trade in and out of Mexico.

Celadon, in fact, reports that more than half its total revenue (51 percent) comes from crossborder movements in and out of Canada and Mexico. Excluding CFI (now a part of Con-way), Celadon is the predominant north-south carrier in the U.S., hauling more freight in and out of Mexico than the next five U.S.-based carriers combined.

The numbers speak for themselves. Celadon generated $502.7 million in operating revenue during fiscal year ended June 30, 2007, and has grown significantly along with the growth of NAFTA trade. To show its growth rate, Celadon reported $414 million revenue in 2006 and $399 million in 2005—much of that growth was because of north-south Mexico trade.

And Celadon is not alone. Surface trade transportation between the United States and its NAFTA partners Canada and Mexico was 4.9 percent higher in 2007 than in 2006, reaching an annual record of $797 billion, according to new DOT’s Bureau of Transportation Statistics (BTS).

Total truck freight among the three NAFTA nations is booming. It has more than doubled from $265 billion 13 years ago to $554 billion last year, according to the BTS statistics. Four industries—electronics, machinery, nuclear reactors and parts, and motor vehicles—account for about $280 billion of that amount, BTS figures show.

Unlike the overall U.S. world trade imbalance, the NAFTA trade is nearly perfectly balanced between imports and exports. For a country with a huge and growing trade imbalance, that fact is important. Largely because of the U.S. thirst for oil imports, we ran a trade imbalance of $763.6 billion in 2006, up from $716.7 billion the year before.

Some trucking executives, already fretting over record-high diesel prices that have trimmed margins in a shaky economy, prefer not to fret over NAFTA’s future, despite what politicians are saying. “It’s hard to determine if this is just political posturing,” says Pitt Ohio President Chuck Hammel. “Will it really change at all? It’s out of our control. It’s like worrying about the price of diesel fuel.”