As a senator, McGovern was an example of modern American liberalism. He became most known for his outspoken opposition to the growing U.S. involvement in the Vietnam War. He staged a brief nomination run in the 1968 presidential election as a stand-in for the assassinated Robert F. Kennedy. The subsequent McGovern–Fraser Commission fundamentally altered the presidential nominating process, by greatly increasing the number of caucuses and primaries and reducing the influence of party insiders. The McGovern–Hatfield Amendment sought to end the Vietnam War by legislative means but was defeated in 1970 and 1971. McGovern's long-shot, grassroots-based 1972 presidential campaign found triumph in gaining the Democratic nomination but left the party badly split ideologically, and the failed vice-presidential pick of Thomas Eagleton undermined McGovern's credibility. In the general election McGovern lost to incumbent Richard Nixon in one of the biggest landslides in U.S. electoral history. Though re-elected to the Senate in 1968 and 1974, McGovern was defeated in his bid for a fourth term in 1980.