Wikipedia: Political activities of the Koch family
Fred C. Koch, the father of Charles and David, was a member of the John Birch Society. He gave a speech in 1963 warning of “a takeover” of America in which Communists would “infiltrate the highest offices of government in the U.S. until the president is a Communist, unknown to the rest of us”. His anti-communism stemmed from his experiences in the Soviet Union, where the very engineers who supported the Bolshevik Revolution and told Fred Koch that they would one day take over the world, were later purged by that same movement.
David H. Koch was a Libertarian Vice-Presidential candidate in 1980. He advocated the abolition of Social Security, the FBI, the CIA, and public schools. Koch put $500,000 into the race, and he and Ed Clark, his presidential running mate, won 1% of the vote—the best Libertarian showing in a U.S. presidential race to date. But the experience caused David Koch to change course: "I had enough," he said. "We are not a nation that debates issues. We vote on candidates' personalities." By 1984, David had parted company with the Libertarian party, because, he said, "they nominated a ticket I wasn't happy with" and "so many of the hard-core Libertarian ideas are unrealistic."
Since then, Charles and David Koch have adopted a much less visible strategy toward advancing their libertarian agenda. In 1986, David Koch helped found the Citizens for a Sound Economy, and has given over $21 million to the Cato Institute.