Not long ago, Douglas Kmiec was an active campaigner for Mitt Romney for president — a plausible fit for the conservative Pepperdine law professor who once served in the Department of Justice Office of Legal Counsel for Presidents Ronald Reagan and George H.W. Bush.

But on Sunday, the former dean of Catholic University of America’s Columbus School of Law made a surprising switch. He wrote in Slate that he had switched to none other than Sen. Barack Obama.