According to the New York Times coverage:
In a statement, the president of U.F.C.W. Local 1500, Bruce W. Both, said that the workers at the Valley Stream store had endured a “campaign of threats, intimidation and illegal acts by Target management.” As a result, he called on the National Labor Relations Board to direct a new election and order Target to cease its “illegal activity.”
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“Target did everything they could to deny these workers a chance at the American dream,” said Mr. Both, of the union local.
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The union filed a complaint with the labor board last month asserting that Target had unlawfully prohibited employees from wearing pro-union buttons and from discussing working conditions on online sites. It also said Target had unlawfully threatened employees with dismissal if they spoke about the union.
In meetings and fliers, Target officials told employees that a union could not guarantee better pay or benefits and that the organization only wanted their dues. In a move that worried numerous workers, the company said there were no guarantees that the store would remain open if the workers unionized.
http://dissentmagazine.org/atw.php?id=478