The Newport Beach resident earned the nomination at the party's weekend convention in Las Vegas. Gary Johnson, the former Republican governor of New Mexico, is party's the pick for president.
Gray announced the news to friends in a letter, which the Pilot published Friday. His Sunday Forum column, It's A Gray Area, will be suspended while he campaigns through November.
"Honestly, I would not do this with anyone except Johnson," Gray wrote. "But after consulting with my wife and other friends and advisors, I have agreed to do so. But I set one condition upon my entering the race: that we would run to win. He absolutely agreed."
Gray is perhaps best known in Orange County for his support of legalizing marijuana and ending the war on drugs, which he views as too costly, violent and unproductive.
His other views, as stated in his recent letter, are generally in accordance with the Libertarian Party's small government platform: reducing government regulation, eliminating deficit spending, using U.S. troops only to protect the national interest, overhauling the tax code, and allowing competition in the school and health-care systems.
Johnson, according to media reports, holds small government views similar to presidential candidate Ron Paul. Johnson supports same-sex marriage and getting the U.S. out of Afghanistan, according to The New York Times.
Before running as a Libertarian, Johnson ran for the 2012 GOP presidential nomination but dropped out just before the Iowa caucuses, according to The Times.