After law school, Spence joined the Democratic Party. He was elected to the South Carolina House of Representatives in 1956 as a Democrat from Lexington County. He was reelected in 1958 and 1960, but on April 14, 1962, Spence announced that he was switching to the Republican Party, having become uncomfortable with the national Democrats' increasingly liberal platform. He also opposed a loyalty oath required by South Carolina Democrats. He was the first Republican to serve in either house of the state legislature since Reconstruction–an example of the political realignment that had begun in South Carolina and in the entire South during the 20th century.