In later decades the former senator remained a symbol, or standard-bearer, of the political left, particularly in relation to the turbulent 1960s and early 1970s when the country was torn by U.S. involvement in the Vietnam War and the corruption and abuse of power of the Nixon administration. Throughout his career, McGovern's positions reflected his own experiences as well as a personal synthesis of the traditions of American liberalism and progressivism. Southern Methodist University historian Thomas J. Knock wrote in 2003 that "[McGovern's] career was extraordinary and historic ... primarily because of his impress as searching and prophetic critic" and that "few political careers offer an alternative understanding of the American Century as compelling and instructive as McGovern's."