Friday is the last day of a union-organizing vote at a Volkswagen plant in Chattanooga, Tenn. At stake is whether the German automaker's sole plant in the U.S. will be represented by the United Auto Workers. But it's also much more than that: The battle being waged in Chattanooga is being billed as a seminal moment that will either pave the way for more labor unions in the South, or affirm the continuation of a "right to work" region that is UAW-free.

Going into the three-day election, the vote was too close too call among the 1,550 workers.

"A vote for unionization at Volkswagen would be a historic victory — not only for the UAW, but for the entire labor movement," says John Logan at Reuters. "It would provide unions with a key victory in the South, even in the face of a lavishly funded external anti-union campaign, and may lead to transformative changes in labor-management relations, especially among European-owned firms." Those notably include the BMW plant in South Carolina and the Mercedes-Benz factory in Alabama.

Those "lavishly funded" salvos are coming from conservative groups like Americans for Tax Reform, the American Legislative Exchange Council (ALEC), and the National Right to Work Committee. Tennessee Republicans have also gotten involved — and this is where things get dicey.

State Sen. Bo Watson (R) threatened to withdraw the state subsidies that helped bring VW to Tennessee in the first place (along with every other foreign automaker in the South and West). "Should the workers choose to be represented by the United Auto Workers," he told the Detroit Free Press, "then I believe additional incentives for expansion will have a very tough time passing the Tennessee Senate." Gov. Bill Haslam (R) made similar, if subtler, statements.

Then, at a news conference on Wednesday — while voting was going on — Sen. Bob Corker (R-Tenn.) played the Mexico card, noting that either the Tennessee plant or one in Puebla, Mexico, will be tapped to make a new line of SUVs. "I've had conversations today and based on those am assured that should the workers vote against the UAW, Volkswagen will announce in the coming weeks that it will manufacture its new mid-size SUV here in Chattanooga," Corker said.

VW, which has tried hard to stay neutral on the unionization issue, publicly contradicted Corker. "There is no connection between our Chattanooga employees' decision about whether to be represented by a union and the decision about where to build a new product for the U.S. market," said Frank Fischer, chief executive of VW Chattanooga.

Corker shot back that "after all these years and my involvement with Volkswagen, I would not have made the statement I made yesterday without being confident it was true and factual." Then he threw a personal jab: "Believe me, the decisions regarding the Volkswagen expansion are not being made by anyone in management at the Chattanooga plant."

It's true that Corker has been in touch with Volkswagen since he was Chattanooga mayor, and that he is on a first-name basis with VW CEO Martin Winterkorn. But VW appears to want the UAW to win, and Corker may have violated U.S. labor laws by attempting to intimidate workers into voting against the UAW. Certainly, his comments have drawn unflattering national attention to the push by Republicans and outside conservative groups to quash the unionization bid.

This is the strongest card that the anti-union side has. The billboards warning that unionization will turn Chattanooga into a postindustrial wasteland — example: "Detroit: Brought to you by the UAW" — don't pass the laugh test. But strongly suggesting that the UAW will kill your livelihood (the Chattanooga plant probably needs a second line of cars to make it) certainly gets workers' attention.

But it's not a very persuasive argument. VW wants to set up a "works council" at the plant — like those at every VW plant except Chattanooga's and two in China — and in order to do that under U.S. law, the Tennessee workers have to have a union. The UAW has agreed to cede significant negotiating power to the works council, a body composed of management and white- and blue-collar workers. VW considers such councils a competitive advantage, because they encourage productivity and strengthen coordination between workers and their corporate bosses. (For an explainer on works councils, which are widespread in Europe, click here.)

The Puebla plant in Mexico has a works council, and it's unionized.

As soon as the votes are counted this weekend, we'll know which way the VW workers decided to go with unionization. My guess is that the annoyance at outside meddling in internal company decisions outweighs the concerns about job security. But if the UAW loses, Corker's interference might invalidate the vote, setting up a do-over. Furthermore, VW and the pro-union workers won't change their minds. They will probably get their works council eventually.

The ham-fisted push by Tennessee's governor, state legislators, and junior U.S. senator has only shown that the heart of the "right to work" South isn't beating as strong as we all thought. The anti-union side has an unexpected weak spot in European automakers, and didn't count on union pragmatism. For the embattled UAW and union movement, that's a big shot of adrenaline and an invitation to come back.

If it turns out that a local auto plant can unionize without sparking catastrophe, well, there are quite a few foreign auto plants in the South. Workers at Nissan plants in Canton, Miss., and Smyrna, Tenn., are currently trying to unionize, despite strong opposition from the Japanese automaker.

"A victory at Volkswagen would signal that the anti-union South — where elected officials have frequently joined with the business community and right-wing organizations to stop workers from organizing — might not be so solid in future years," says Reuters' Logan. "Most importantly, a UAW victory would show that even billionaire anti-union zealots can be beaten."