His legislative work during his career as a Senator facilitated a vast expansion of modern liberalism in the United States. He fathered the 1960s environmental movement which culminated in the passage of the Clean Air Act of 1970 and Clean Water Act of 1972, hallmarks of international environmental policy. A supporter of the civil rights movement, Muskie rallied support for the Civil Rights Act of 1964, the creation of Martin Luther King Jr. Day and tapered Richard Nixon's "Imperial Presidency" by advancing New Federalism. Muskie ran with Humphrey against Nixon in the 1968 presidential election, only to lose by 0.7 percentage points—one of the narrowest margins in U.S. history. He would go on to run in the 1972 presidential election where he secured 1.84 million votes in the primaries coming in fourth out of 15 contesters. The release of the controversial "Canuck letter" derailed his campaign and sullied his public image with Americans of French-Canadian descent.