Victor B. Geller, Orthodoxy Awakens: The Belkin Era and Yeshiva University, pp. 258-259:
In 1957, the Poage Bill was introduced in the United States Congress. Actively supported by the humane societies, the bill proposed the outlawing of the prevailing "hoisting and shackling" method used in slaughterhouses. The tone and further provision of the bill were viewed as a threat to kosher shechitah (slaughter).
In a rare demonstration of unity, the entire Jewish community rallied to fight the Poage Bill... At a critical moment, a prominent New York member of the RCA learned that Rav [Aharon] Kotler had changed his mind. He was going to break ranks and would not sign the statement [opposing the bill]. After verifying the truth of the report he had received, the RCA member called Rav Soloveitchik to tell him of this latest development. The Rav responded by asking the caller to come to Boston immediately. As soon as the New York rabbi arrive in Boston, the Rav said to him, "I am going to call Rav Kotler on the telephone. I want you to stand by to hear the results of my call."
When Rav Soloveitchik announced himself, Rav Kotler, at first taken aback, responded with warmth and deference. Rav Soloveitchik, however, was all business. He told Rav Kotler that he had received troubling news. He asked Rav Kotler if the report of his change of mind on the Poage Bill was true. Rav Kotler became uncomfortable. After some hesitation and equivocation, he admitted that he was having second thoughts.
Rav Soloveitchik responded in a very direct and firm tone. He told Rav Kotler, "You must sign. And don't try to give me any halachic reasons why you won't. We both know that I could refute them." The conversation ended with Rav Kotler saying, "Well, if that's he way you feel, I will sign."
 Interview with anonymous RCA officer, August 1995.