Final answer:
The Wagner Act of 1935, also known as the National Labor Relations Act, places federal government support behind employee efforts to organize and bargain collectively, establishing the National Labor Relations Board to enforce its provisions.
Step-by-step explanation:
The act that places the protective power of the federal government firmly behind employees' efforts to organize and bargain is the Wagner Act of 1935, officially known as the National Labor Relations Act. This act was a cornerstone of New Deal legislation and served to reaffirm workers' rights that had been provisioned under the National Industrial Recovery Act.
Specifically, the Wagner Act not only protected the rights of workers to form unions and collectively bargain with employers, but it also prohibited employers from engaging in unfair labour practices, such as discrimination against union members, and it established the National Labor Relations Board (NLRB) to enforce its provisions and to arbitrate disagreements between unions and employers.