The U.S. Senate election, 1966 was an election on November 8, 1966 for the United States Senate which occurred midway through the second and first full term of President Lyndon Johnson. With divisions in the Democratic base over the Vietnam War, and with the traditional mid-term advantage of the party not holding the presidency, the Republicans took three Democratic seats. Despite Republican gains, the balance remained overwhelmingly in favor of the Democrats, who retained a 64–36 majority. This was also the first election that occurred after the Voting Rights Act of 1965 became law.