The call came into The National Enquirer's Los Angeles tip line — the kind advertised in the supermarket tabloid with the promise "We'll Pay Big for Your Celebrity Gossip" — in late September 2007. The message was that a woman named Rielle Hunter had been hinting at an affair with John Edwards, then a candidate for president.

Within an hour, the tip was on the desk of Barry Levine, The Enquirer's executive editor in New York. His readers didn't care about politics for politics' sake, not as long as there were rocky Hollywood marriages to be covered and celebrity cellulite photos to be snapped. But Mr. Levine was intrigued when he looked up Mr. Edwards on Google and found a poll saying that the candidate and his wife, Elizabeth, had one of the most admired marriages of all the candidates.