The United Automobile Workers union unexpectedly announced on Monday that it was dropping its effort to have a new unionization vote ordered at the Volkswagen plant in Chattanooga, Tenn.

The union lost a vote at the plant in February, 712 to 626, and soon afterward it asked the National Labor Relations Board to order a new election, asserting that anti-union statements and threats by Tennessee lawmakers had prevented a fair election.

Bob King, the U.A.W.’s president, said his union was withdrawing its appeal based on the belief that the labor board’s adjudication process “could drag on for months or even years.”

The vote was a major defeat for the U.A.W. because Volkswagen, unlike most American companies faced with unionization drives, did not even oppose the effort. If the union had won the vote, the plant would have become the first foreign-owned auto factory in the South to be unionized, and many said it could pave the way to unionizing the Daimler-Benz plant in Vance, Ala., and the BMW plant in Spartanburg, S.C.