Tuhia he tohutoro mō tēnei wāhanga - Mai i te 1923 ki te 1924, i noho a Phelps ki te tūranga o te Kaiwhakahaere Tuarua mo nga Take Veterans mo New York City. I mahi ia hei mema Republican o te New York State Assembly mai i Greenwich Village i te 1924, 1925, 1926, 1927 me te 1928. I te tau 1928, i rere ia mo te whakaingoatanga mo te Whare Kawana o te United States, engari i ngaro te tuatahi ki a Ruth Baker Pratt, ko ia te wahine tuatahi o te kaunihera o New York. Whai muri i te 1932 Republican National Convention, ka noho a Phelps hei Democrat, ka haere ki te 1936, 1956
, me te 1960 Democratic National Conventions hei mema. He mema ano ia o te Whare Kaunihera o te Kaunihera (New York Co., 3rd D.) i te 1937 me te 1938; me te mema o te New York State Senate (13th D.) mai i te 1939 ki te 1942, e noho ana i te 162nd me te 163rd New York State Legislatures.