The United Auto Workers could be forced to reconsider its efforts to organize at foreign-owned factories in the U.S., a labor expert said, as the union vowed to keep fighting after losing a closely watched vote at Volkswagen AG’s Tennessee plant.

Workers in Chattanooga voted 712-626 on Friday against joining the UAW after three days of balloting that drew intense opposition from elected officials. The company didn’t fight the UAW campaign, which may have cost as much as $5 million and lasted more than two years, said Gary Chaison, a labor law professor at Clark University in Worcester, Mass.

A victory would have added momentum as the UAW seeks to sign up workers at a Daimler AG factory in Vance, Ala., and other foreign automakers, known as transplants, that settled in the U.S. South to take advantage of tax breaks, non-union labor and easy access to markets. Now the UAW must regroup, he said.

“This is a time for soul-searching at the UAW and within the American labor movement,” Chaison said Saturday in an interview. “This was the ideal situation and they know that. They might just give up on transplants.”

In Germany, representatives of Volkswagen’s works council – an employee- management body that tries to resolve disputes at most large German companies – said they would still press to establish a council at the Tennessee facility.

The UAW may have misjudged the intensity of an anti-union drive by groups and Tennessee leaders such as Gov. Bill Haslam and Sen. Bob Corker, both Republicans, said Joseph Farelli, a lawyer with the New York firm of Pitta & Giblin who represents labor unions.

“You had a lot of third-party organizations really campaigning hard against the union,” Farelli said in an interview.

AFL-CIO President Richard Trumka, leader of the nation’s biggest labor federation, said “the closeness of the (Chattanooga) results and the courage and tenacity of union supporters prove that this election is a minor setback, and not a permanent defeat.”

The loss may prompt the UAW to look for new members among hotel workers, university teaching assistants or others outside the automobile industry, Chaison said.