He was the editor of the Communist Party's newspaper, "The Clarion", before fleeing to the United States with other party leaders in 1940 when the party was again declared illegal. When the Soviet Union became an ally later in the war as a result of the German invasion of the USSR, those party leaders such as Carr and Tim Buck who had gone underground turned themselves into the authorities in 1942 and were released after ten days on the promise that they would refrain from communist activities. As a result, the Labor-Progressive Party was formed in 1943 as a legal front for the party - Carr became its national organizer.