In 1860, he was elected reporter of the Indiana Supreme Court. Harrison was an active supporter of the Republican Party's platform and served as Republican State Committee's secretary. After Garfield's election as president in 1880, his administration offered Harrison a cabinet position, but Harrison declined in favor of continuing his service in the U.S. Senate.Harrison served in the Senate from March 4, 1881, to March 3, 1887, and chaired the U.S. Senate Committee on Transportation Routes to the Seaboard (47th Congress) and the U.S. Senate Committee on Territories (48th and 49th Congresses).In 1881, the major issue confronting Senator Harrison was the budget surplus. Harrison returned to Indianapolis and resumed his law practice, but stayed active in state and national politics. Harrison appointed four justices to the Supreme Court of the United States. The first was David Josiah Brewer, a judge on the Court of Appeals for the Eighth Circuit.