(CNN) - John Bolton, the former U.S. permanent representative to the United Nations, endorsed presidential candidate Mitt Romney Wednesday.
Bolton made the endorsement on Fox News Channel, where he is a paid contributor.
“I followed the way that the William F. Buckley, Jr. test: find the most conservative candidate capable of getting elected, and there are obviously two variables there,” Bolton said on Fox News’ “On the Record w/ Greta Van Susteren.”
“In the words of the old song ‘Give Me That Old Time Religion,’ Romney is conservative enough and I think that’s critical.”
Bolton served in the administrations of former Presidents Ronald Reagan and George H.W. Bush before former President George W. Bush appointed him the U.N. role.
Bolton endorsed Sen. John McCain's presidential bid in February 2008, and briefly flirted with a presidential run for himself in 2011.
Bolton's endorsement of Romney was first reported by the Wall Street Journal.