Mack Trucks, Inc. (Mack) announced its intention to sell a factory branch that employed a unionized work force. In response, a group of the branch’s managers formed Allentown Mack Sales & Service, Inc. (Allentown) (plaintiff). Allentown purchased the branch’s assets and began operating the factory independently. Allentown hired 32 of the branch’s former Mack employees, several of whom had made statements indicating a lack of employee support for the union. Following the acquisition, the union asked Allentown to recognize it as the employees’ union. Allentown declined, asserting uncertainty that the union had employee support. Allentown conducted a poll of employee support for the union. After losing the vote, the union filed a charge of unfair labor practice with the National Labor Relations Board (NLRB) (defendant). Relying on statements of seven of the 32 Allentown employees, an NLRB administrative law judge (ALJ) concluded that, as Mack’s successor in interest, Allentown had assumed Mack’s relationship to the union and had failed to demonstrate the objective reasonable doubt needed for a poll of employee support. The NLRB ordered Allentown to continue to recognize the union as the employees’ collective-bargaining representative. Allentown petitioned the United States Court of Appeals for the District of Columbia for review. The court of appeals affirmed the NLRB’s order. The United States Supreme Court granted certiorari to determine whether the NLRB’s fact-finding was supported by substantial evidence.