In 1899, Ransdell was elected as a
Democrat to the
Fifty-sixth Congress to fill the vacancy created by the death of
Samuel Thomas Baird. He won his first full term in Congress in 1900, having defeated the
Republican businessman
Henry E. Hardtner of
Urania in
La Salle Parish, 6,172 votes (90.8 percent) to 628 (9.2 percent). Hardtner was the last Republican to contest the seat until 1976, when
Frank Spooner of
Monroe waged a strong but losing challenge to the Democrat
Jerry Huckaby of
Ringgold in
Bienville Parish. By 1910, Hardtner had switched to Democratic affiliation and served for two years in the
Louisiana House of Representatives as the first member ever from La Salle Parish. From 1924 to 1928, Hardtner was a
state senator. Ransdell served in the House from August 29, 1899, to March 3, 1913. He was not a candidate for renomination in 1912, having instead been elected by the
Louisiana State Legislature to the
United States Senate, prior to the passage of the
Seventeenth Amendment to the United States Constitution. In 1918, he defeated future U.S. Senator
John H. Overton of Alexandria in a disputed vote. Ransdell won his third term in the Democratic
primary election in 1924, having defeated
Lee Emmett Thomas, the
mayor of
Shreveport, 104,312 (54.9 percent) to 85,54 (45.1 percent). Huey Pierce Long Jr., while himself running for a second term on the regulatory Louisiana Public Service Commission spent more time supporting Ransdell for the Senate than he did his own campaign in which he carried all twenty-eight parishes in his district. Long was particularly motivated by his fierce opposition to Mayor Thomas though Long was then a resident of Shreveport. Ransdell was a US senator from March 4, 1913, to March 3, 1931. But in 1930
Governor Huey Long ran in the Democratic primary against him for the seat and won. With 149,640 votes (57.3 percent), Long toppled Randsell, who polled 111,451 (42.7 percent). Long was elected in the general election without Republican opposition. Ransdell had appeared in 1927 at a Long political rally in Lake Providence, where his younger brother introduced Long. District Attorney
Jefferson B. Snyder, another long-term advocate of planter interests, sat on the stage. Snyder had not really favored Long so much as he was convinced that Long would defeat his chief opponent, U.S. Representative
Riley J. Wilson, the favorite of most planter interests, and Snyder wanted to influence the new governor. At the rally, Huey Long began "a harangue that castigated their closest friends and political allies and the old establishment itself, of which these men were a part." Particularly outraged at Long's treatment of the Randsdells was state Senator
Norris C. Williamson of East Carroll Parish, the vice-president of the Constitutional League of Louisiana. He would not
compromise with the Longs and retired to private life in 1932, rather than face likely defeat by the Long
faction.
T. H. Harris, the long-term Louisiana state superintendent of education, called Ransdell "one of the most lovable and distinguished citizens of the United States. [Yet] the people elected Long to the Senate because they believe that he can be of more use to them there. The people trust Long. I find it mighty easy to get on with Governor Long. I have seen the school appropriations increased by $1.9 million during the past two years. .." Ransdell was chairman of the Committee on Public Health and National
Quarantine (
Sixty-third through
Sixty-fifth Congresses) and a member of the Committee on Mississippi River and Its Tributaries (
Sixty-sixth Congress). It was in this capacity that Ransdell sponsored the
Ransdell Act, which created the
National Institutes of Health. ==Later years and legacy==