Workers at two Mercedes-Benz factories near Tuscaloosa, Ala., voted on Friday against joining the United Automobile Workers, a stunning blow to the union’s campaign to gain ground in the South, where it has traditionally been weak.
The defeat came after Kay Ivey, Alabama’s governor, and other Republican leaders argued that a pro-union vote would choke off the investment that has transformed the state into a major auto producer. Hyundai and Honda also have large factories in Alabama that the U.A.W. is trying to organize.
The vote took on national significance as a test of whether the U.A.W. could build on a string of recent victories and gain ground in a state whose elected officials have been hostile to organized labor. The union has said it wants to organize every automobile factory in the United States, expanding its membership to include the employees of companies like Toyota and Tesla.
But the loss at the Mercedes plants will almost surely slow down the union’s campaign and probably force it to do more spadework to secure the support of workers before seeking to hold elections at other auto plants. Union leaders will want to spend time figuring out how best to counter the messages and tactics of local lawmakers and company executives.
“It hurts to lose, no doubt,” Elizabeth Shuler, president of the A.F.L.-C.I.O., said on Friday. “But we see it not as a loss, but a temporary setback. Workers will persevere no matter what it takes.”
Mercedes workers voted 56 percent to 44 percent against joining the union, according to the National Labor Relations Board, which oversaw the election. Close to 4,700 ballots were cast, representing a large majority of the 5,075 employees who were eligible to vote.
Auto executives and conservative lawmakers are likely to closely study the vote at Mercedes to figure out the best approaches to fend off the U.A.W. and other unions in future contests and to deter union campaigns from the get-go.
The South has become an important battleground. States like Georgia, South Carolina and Tennessee are attracting much of the billions of dollars that automakers and suppliers are investing in electric vehicle and battery factories. The U.A.W. wants to represent workers at those factories.
Mercedes produces sport utility vehicles at a factory in Vance, Ala., and battery packs for electric vehicles at a plant in nearby Woodstock. Polling had been underway all week at the two factories.
“We thank all team members who asked questions, engaged in discussions and, ultimately, made their voices heard on this important issue,” the company said in a statement on Friday.
In a campaign conducted largely by word of mouth, union activists argued that in addition to better pay and benefits, the U.A.W. would protect Mercedes workers from abrupt changes in their schedules and long shifts, including on weekends.
“If it wasn’t for us building those cars, you wouldn’t be putting the money that you’re putting in your pockets,” said Kay Finklea, who works in quality control at Mercedes and campaigned for the union. “So treat us with dignity, treat us with respect and pay us.”
But activists acknowledged that many workers who were unhappy with working conditions at Mercedes were also reluctant to join the union, swayed by warnings from company executives and politicians that membership would lead to onerous dues and loss of control over their jobs.
Mercedes tried hard to block the union. Last month, in an apparent attempt to address employee complaints, the company shook up local management, appointing Federico Kochlowski as chief executive of the German company’s U.S. unit.
Mr. Kochlowski, who has worked at Mercedes for about 20 years in various manufacturing positions in China, Mexico and the United States, acknowledged that there were problems at the Alabama plants and promised to make improvements. “I understand that many things are not OK,” he said in a video posted by Mercedes online. “Give me a shot.”
Union activists noted that Mr. Kochlowski had already been a member of top management and interpreted his appointment as a last-minute attempt to fend off the U.A.W.
The U.A.W. has filed six charges of unfair labor practices against Mercedes with the labor relations board, saying the company disciplined employees for discussing unionization at work, prevented organizers from distributing union materials, conducted surveillance of workers and fired workers who supported the union.
Mercedes denies the claims.
Previous attempts by the U.A.W. to represent workers at Mercedes and other auto manufacturers in the South have failed. But the U.A.W. is stronger than it has been in years after winning a unionization vote at a Volkswagen plant in Tennessee last month after losing two previous elections at that plant. The union also won hefty pay raises last year for workers at Ford Motor, General Motors and Stellantis, the parent company of Chrysler, Jeep and Ram.
Mercedes workers who support joining the U.A.W. said they would keep fighting.
“Mercedes is going to be unionized,” Robert Lett, who works in the Woodstock battery factory and campaigned for the union, said ahead of the vote. “It doesn’t matter if it’s Friday or in the future. There’s too much frustration there for us to not eventually unionize.”