Lewis was a Republican, but he played a major role in helping Democrat Franklin D. Roosevelt win a landslide victory for the US Presidency in 1936. He was an isolationist, and broke with Roosevelt in 1940 on FDR's anti-Nazi foreign policy. Lewis was an effective, aggressive fighter and strike leader who gained high wages for his membership while steamrolling over his opponents, including the United States government. Lewis was one of the most controversial and innovative leaders in the history of labor, gaining credit for building the industrial unions of the CIO into a political and economic powerhouse to rival the AFL. But during World War II, he was widely criticized by calling nationwide coal strikes, which critics believed to be damaging to the American economy and war effort.