Former Sen. John Edwards (D-N.C.) may not be the only 2008 Democratic presidential primary candidate whose staff covered up an extra-marital affair. According to a new book out this week, then-Sen. Hillary Clinton's (D-N.Y.) did, too.

An excerpt posted at The Atlantic from "Game Change," written by reporters John Heilemann and Mark Halperin, describes a "war room within a war room" at the Clinton campaign made up of Hillary's closest aides, tasked with investigating rumors of infidelity involving Clinton's husband, former president Bill Clinton.

Bill Clinton has admitted to having at least one extra-marital affair with former White House staffer Monica Lewinsky, but rumors of infidelity have dogged the former president through much of his career.

While much of the gossip in 2008 reportedly turned out to be false, the authors write that, "The stories about one woman were more concrete, and after some discreet fact-finding, the group concluded that they were true: that Bill was indeed having an affair -- and not a frivolous one-night stand but a sustained romantic relationship."

From that point forward, the authors claim, those staffers who knew about the relationship lived in constant fear of it being discovered.

Despite their success at keeping the affair under wraps, Clinton ultimately lost the Democratic nomination to President Barack Obama.

The book doesn't name the woman, although tabloid reports in mid-2008 alleged that Clinton was romantically involved with woman who lived near the couple's home in Chappaqua, N.Y.

"Game Change" officially goes on sale Tuesday.