Following the United States' entry into the war in Europe in the spring of 1917, Magnes switched all his attention to campaigning against it. He became one of the movement's high-profile leaders. Like most of its leaders his sympathies were with the working classes. People such Eugene Debs who was sentenced to ten years in prison for his activities; Norman Thomas; Roger Nash Baldwin; Scott Nearing; Morris Hillquit, who took 22% of the vote in New York's Mayoral elections on an anti-war platform; and Oswald Garrison Villard. Most of these men were involved in what became the People's Council of America for Democracy and Peace with Magnes its first chairman. On 30 May 1917 he gave the keynote address to a mass meeting of fifteen thousand people in the Madison Square Gardens. A follow-up meeting in Minneapolis was banned and hastily re-convened in Chicago but with a military force threatening to break it up. Magnes moved home in Connecticut because of hostility from his neighbours and was interviewed by an agent from the Department of Justice. One of his colleagues from the "Joint", B. D. Bogen, was questioned by the Attorney General about Magnes' activities. Magnes worked with the newly formed Civil Liberties Bureau which defended pacifists and conscientious objectors. In America more than 2,000 prosecutions were brought against war-resisters under the Conscription Act or the Espionage Act; Magnes avoided prosecution since he was over conscription age.