One of his most noteworthy campaigns was conducted on behalf of The Great Atlantic and Pacific Tea Company (A&P), a grocery company that was the world's largest retailer by far. In 1937, A&P, which had never engaged in political matters before, hired Byoir to help it fight the powerful anti-chain-store movement, which sought to break up big chains in order to protect independent retailers and wholesalers. Working behind the scenes, Byoir organized a campaign to highlight the benefits of chains in reducing consumer prices. The campaign burst into public view on September 15, 1938, when 1,600 publications ran a full-page advertisement headlined "A Statement of Public Policy by the Great Atlantic & Pacific Tea Company." The advertisement criticized a bill introduced by U.S. Rep. Wright Patman of Texas to impose punitive taxes on chain stores. The bill was blocked, and the power of the anti-chain movement began to wane. Byoir remained an influential advisor to A&P for many years.