Kenney was the State Librarian from 1879 until 1881. He was also Captain in the National Guard from 1880 until 1889, and Adjutant General of the state from 1887 until 1891. In 1896 he became a member of the Democratic National Committee. He was elected to the U.S. Senate on January 19, 1897. He filled the vacancy in the term commencing March 4, 1895, caused by the ongoing
Addicks controversy. During this term, he served with the Democratic minority in the 54th, 55th, and 56th Congress. The Democrats were unable to secure his reelection in 1901, and the seat became vacant again. In all, he served from January 19, 1897, until March 4, 1901, during the administration of U.S. President William McKinley. Following his term, Kenney resumed the practice of law in Dover. Later, during the World War I, he served in the
Judge Advocate General's Department. In 1921 he was elected counsel to the Delaware House of Representatives, elected prosecuting attorney by the levy court of Kent County, and appointed a member of the State board of supplies. He was also member and secretary of the State public lands commission from 1913 until 1929. ==Death and legacy==