Horne was a United States Army Air Forces pilot during World War II.

Horne was the second post-Reconstruction person to serve as both speaker of the House and president of the Senate, after Ion Farris.

He was credited as "chiefly responsible for keeping the state capital in Tallahassee against an effort to move it [south] to Orlando".

[2] Horne left the legislature after an unsuccessful run for the Democratic U.S. Senate nomination in 1974, working as a lawyer and a lobbyist.

Horne was tried and acquitted in 1985 on charges of money laundering when federal investigators alleged that he had smuggled marijuana into the United States from the Cayman Island on the twin-engine airplane he piloted.