DETROIT, May 13 Reuters Workers at a MercedesBenz plant in Alabama began voting Monday on whether to join the United Auto Workers union, a significant test of whether the labor group can maintain momentum in the historically antiunion American South.

A union victory at the plant, weeks after a resounding win at a Volkswagen VOWGp.DE factory in Tennessee, would be a watershed moment for the UAW as it seeks to organize more than a dozen automakers across the nation and add to its dwindling ranks.

The campaign at Mercedes has been much more contentious. The company has urged workers to vote no, according to fliers and signage viewed by Reuters. Mercedes also hired antiunion firms to speak with workers, plant employees said.

Mercedes has rejected claims it prevented union organizing efforts in Alabama. A spokeswoman said the company respects employee unionizing efforts and is ensuring every worker has a chance to vote by secret ballot while having the information needed to make an informed choice.

The 5,200 employees at the assembly plant and nearby battery factory will cast ballots this week, with final results expected Friday.

UAW President Shawn Fain has spent more than a year strategizing his path to win over nonunion auto workers, and it all began with new labor contracts in Detroit.

Fain became UAW president in March 2023 and led the union through its first simultaneous strike against the Detroit Three automakers General Motors, Ford and Jeepmaker Stellantis. The…