The United Auto Workers has dropped a challenge to a failed union-organizing vote at a Volkswagen plant in Tennessee earlier this year. In a blow to organized labor, Volkswagen workers in Chattanooga rejected unionization, declining to make their plant the first unionized foreign-owned car factory in the United States. The union faced intense opposition from Republican lawmakers who suggested the plant might miss out on future subsidies or on a new SUV line if the union was approved. The National Labor Relations Board was due to hear the UAW’s challenge on Monday, but the union dropped its bid just before the hearing was set to begin. The UAW says it made the decision after top Republicans and anti-union activists vowed to ignore subpoenas to testify.