He was elected to the Louisiana state Senate in 1928 in the wake of
Huey Long's
landslide victory in the gubernatorial election. He defeated the anti-Long incumbent, former
Republican Henry E. Hardtner of
La Salle Parish. Allen served as Long's floor leader in the Senate; he was also appointed by the governor as chairman of the Louisiana Highway Commission, serving from 1928 until 1930. His appointment was legally challenged. In the litigation that reached the
Louisiana Supreme Court, it ruled that holding both legislative and executive positions simultaneously was unconstitutional. Allen resigned as chairman. Allen was elected governor in the shadow of Huey Long, who had resigned after being elected as US Senator from Louisiana and relocated to Washington, D.C.. Allen was considered a
political stooge for former governor Long. His brother
Earl Long once joked that a leaf blew into Allen's office one day and that he signed it, thinking it was legislation from Long. During Allen's time as governor, a number of progressive reforms were carried out in areas such as education and working conditions. ==Death and honors==