More than 5,000 Mercedes-Benz workers in Alabama are voting this week on whether to join the United Automobile Workers union, a decision both supporters and opponents say will have consequences far beyond two factories near Tuscaloosa where the German carmaker churns out luxury sport utility vehicles and batteries for electric cars.

Conservative political leaders have portrayed the union campaign to organize Mercedes workers as an assault by outsiders on the region’s economy and way of life. The vote tally is expected to be released by federal officials on Friday.

Six Southern governors, including Kay Ivey, an Alabama Republican, issued a statement last month criticizing unions as “special interests looking to come into our state and threaten our jobs and the values we live by.” Alabama recently passed a law intended to discourage union organizing.

For the union, a win would add to a string of victories in the South, where organized labor has traditionally been weak, and provide momentum to the U.A.W.’s efforts to win over workers at other nonunion automakers like Hyundai, Toyota, Honda and Tesla.

If the U.A.W. loses, it could sharply slow down a campaign by the union’s president, Shawn Fain, to organize auto and battery plants across the country. That effort began after the union last fall reached new contracts with hefty pay raises and other benefits for workers at General Motors, Ford Motor and Stellantis, the parent company of Chrysler, Jeep and Ram.

In Alabama, which was a crucible of the civil rights movement, union organizers and supporters cast the Mercedes campaign as part of a decades-long struggle to dismantle an economic system based on exploitation of poor people.