 In the early 1960s , the topic of civil rights was coming to national prominence with sit @-@ ins and marches organized by Martin Luther King Jr. and other black leaders . In 1963 , President John F. Kennedy sent a comprehensive civil rights bill to Congress , based largely on the ideas that Humphrey had been placing before the Senate for the previous fifteen years . The bill passed the House in early 1964 , but passage through the Senate was more difficult , due to southern segregationists who filibustered for 75 days . Finally , in June 1964 , the Civil Rights Act of 1964 became law . Humphrey called this his greatest achievement . Lyndon B. Johnson recruited Humphrey for his running mate in the 1964 presidential election , and Humphrey became Vice President of the United States . Governor Karl Rolvaag ( DFL ) appointed Walter Mondale to fill Humphrey 's Senate seat . Humphrey voiced doubts about the 1965 bombings of North Vietnam , which alienated him from Johnson . He later defended Johnson 's conduct of the Vietnam War , alienating himself from liberals , who were beginning to oppose the war around 1967 . In the 1968 presidential election , Humphrey ran against Richard Nixon and Independent candidate George Wallace and lost the popular vote by only 0 @.@ 7 % . Humphrey later returned to the Senate in 1971 after Eugene McCarthy left office . 
