The United Auto Workers union seems to be adopting what is increasingly becoming the tactic of choice on the left—silencing those who disagree with them.

The IRS scandal is about silencing political discourse disagreeable to the administration. Louisiana Governor Bobby Jindal shocked Democrats by daring to disagree with President Obama last week after a White House meeting.

Now the UAW is claiming that a vote against the union in a Chattanooga, Tenn. Volkswagen plant deserves a redo because Tennessee Senator Bob Corker spoke out against the union before the vote.

Yes—the union, which campaigned at the plant for two years before the vote, enjoying unfettered access to employees, is claiming that the senator didn’t have the right to speak out against the union. The union complains that “outside forces”—that would be Tennessee politicians who oppose the union—unfairly interfered by voicing their objections.

Corker is a former mayor of Chattanooga who worked to create the industrial park where the Volkswagen plant is and who, as a senator, also lobbied Volkswagen to bring its plant to Tennessee.

Corker writes in today’s Wall Street Journal that he doesn’t believe that the UAW had the best interests of the workers at heart:

In 2008, when the "Detroit Three" auto makers came to Congress looking for financial assistance, I became deeply involved in negotiations, trying to protect taxpayers before any federal funds were expended. During those intense talks, it became quickly apparent through direct negotiations with the UAW's top leadership that its main interest was its own survival. The employees they represent and their affiliated companies were way down the list.

It was with this perspective—and my belief that part of my job is to speak out on issues important to my state—that I joined community leaders and a number of employees in Chattanooga this winter to ensure that VW workers who would be making this important decision had a broader point of view than they were getting inside the plant from UAW operatives.

When the workers voted against the UAW, the union filed a complaint with the National Labor Relations Board claiming that Corker and others should not have been allowed to comment. President Obama urged the workers to adopt the union, a fact omitted from the UAW complaint.

Corker writes:

If the National Labor Relations Board upholds these objections, it would be an unprecedented assault on free speech. In every similar case where a company has remained neutral in a union-election drive, members of Congress on both sides of the aisle have voiced their opinions. The NLRB has ruled repeatedly that public officials have the right to make statements taking sides in a union election, and that those statements do not justify overturning the outcome of that election.

The stakes are high. The UAW has publicly stated that its very survival depends on organizing foreign auto manufacturers. Mr. Obama raised the ante when he weighed in on behalf of the union during the voting period. The National Labor Relations Board soon will have to decide whether to follow years of precedent and let the vote of the workers stand—or whether it will try to muzzle elected officials and prevent them from weighing in on issues of critical importance to the communities they represent, possibly because the members of the NLRB did not like the outcome of a vote by workers.

The nation will be watching this ruling closely.