 In 1964, Mansfield, as Senate Majority Leader, filed a procedural motion to have the Civil Rights Act of 1964 discussed by the whole Senate rather than by the Judiciary Committee, which had killed similar legislation seven years earlier.Mansfield voted in favor of the Civil Rights Acts of 1957, 1960, 1964, and 1968, as well as the 24th Amendment to the U.S. Constitution and the Voting Rights Act of 1965, but did not vote on the confirmation of Thurgood Marshall to the U.S. Supreme Court.He hailed the new Richard Nixon administration, especially the "Nixon Doctrine" announced at Guam in 1969 that the US would honor all treaty commitments, provide a nuclear umbrella for its allies, and supply weapons and technical assistance to countries where warranted without committing American forces to local conflicts.