 On November 1 , 1946 , Vermont Governor Mortimer R. Proctor appointed Flanders to the U.S. Senate as a Republican to complete the term of Republican Senator Warren Austin . Austin had just been appointed by U.S. President Harry S. Truman as Ambassador to the United Nations . Flanders 's appointment gave him seniority over the freshman Senators who would be elected four days later on November 5 . Flanders ran for the office then , as well , and was elected to a full term . He was overwhelmingly reelected in 1952 . He declined to seek a third term in 1958 . 
