After the war, Connor began involvement in political issues in 1868, becoming an assessor of the Internal Revenue, as well as serving as the regional collector of internal revenue in 1874. In 1875, he was elected governor of Maine as a Republican. He appointed James G. Blaine to the vacant Senate seat. During his time in politics, Connor advocated civil service reform, and supported the resumption of specie payments. Connor was also responsible for promoting a free public school system, in which he was successful. Connor left office on January 8, 1879, after failing to win reelection.
Subsequently, he was United States pension agent from 1882 to 1886. Connor was active in veterans affairs, and in 1890 became president of the Society of the Army of the Potomac. From 1896 to 1899, he was the senior vice-commander-in-chief of the Military Order of the Loyal Legion of the United States. In 1897, he was again appointed as a pension agent. His address on Hannibal Hamlin was published in 1909. Connor remained a prominent figure in Maine politics, and also served as president of the Northern Banking Company.
Herringshaw, Thomas William. 1909. "Connor, Seldon". Herringshaw's National Library of American Biography : Contains Thirty-Five Thousand Biographies of the Acknowledged Leaders of Life and Thought of the United States; Illustrated with Three Thousand Vignette Portraits.