Five who dared to switch

Arthur Koestler

Old school: Crusading communist journalist in the 1930s

New school: Crusading anti-communist novelist in the 1940s

Fallout: His 1941 novel exposing Soviet purges, “Darkness at Noon,” met with disbelief from old comrades.

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Whittaker Chambers

Old school: New York’s “hottest literary Bolshevik” and a communist agent in the 1930s

New school: A staunch anti-communist editor and author of the 1952 memoir “Witness,” about his turnaround

Fallout: Friends and allies decried his testimony before the House Un-American Activities Committee condemning Alger Hiss as a communist spy; evidence released over three decades vindicated his charges against Hiss.

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Christopher Hitchens

Old school: A socialist denouncer of Henry A. Kissinger’s realist approach to foreign policy

New school: A neoliberal idealist of the Iraq war

Fallout: His belief that 9/11 revealed the left’s weaknesses lost him friends and loyal readers.

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David Horowitz

Old school: A left-radical Ramparts writer and friend to Black Panther Huey Newton in the 1960s and ‘70s

New school: A conservative critic of academics, the politically correct and the postmodernists through his think tank, magazines and liberal-baiting websites.

Fallout: Now a fixture on the right, Horowitz is decried by the left as a polemicist and a racist for his views on multiculturalism and civil rights.

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Zell Miller

Old School: The former Democratic senator from Georgia

New School: The former Democratic senator from Georgia who voted Republican and endorsed President Bush in a fire-breathing 2004 convention speech

Fallout: Republicans happily adopted Miller even though he wouldn’t switch parties; Democrats let him go as another Southern defector.