Does Judith Regan Have the Goods on Rudy Giuliani?

New Yorkers who remember Rudy Giuliani as the bullying New York mayor, not as the terminally cheerful "America's Mayor" cooing to babies in New Hampshire, have always banked on one certainty: his presidential candidacy was so preposterous it would implode before he got anywhere near the White House.

Surely, we reassured ourselves, the all-powerful Republican values enforcers were so highly principled that they would excommunicate him because of his liberal social views, three wives and estranged children. Or a firewall would be erected by the firefighters who are enraged by his self-aggrandizing rewrite of 9/11 history. Or Judith Giuliani, with her long-hidden first marriage and Louis Vuitton 'tude, would send red-state voters screaming into the night.

Wrong, wrong and wrong. But how quickly and stupidly we forgot about the other Judith in the Rudy orbit. That would be Judith Regan, who disappeared last December after she was unceremoniously fired from Rupert Murdoch's publishing house, HarperCollins. Last week Ms. Regan came roaring back into the fray, a silver bullet aimed squarely at the heart of the Giuliani campaign.

Ms. Regan filed a $100 million lawsuit against her former employer, claiming she was unjustly made a scapegoat for the O. J. Simpson "If I Did It" fiasco that (briefly) embarrassed Mr. Murdoch and his News Corporation. But for those of us not caught up in the Simpson circus, what's most riveting about the suit are two at best tangential sentences in its 70 pages: "In fact, a senior executive in the News Corporation organization told Regan that he believed she had information about Kerik that, if disclosed, would harm Giuliani's presidential campaign. This executive advised Regan to lie to, and to withhold information from, investigators concerning Kerik."

Kerik, of course, is Bernard Kerik, the former Giuliani chauffeur and police commissioner, as well as the candidate he pushed to be President Bush's short-lived nominee to run the Department of Homeland Security. Having pleaded guilty to two misdemeanors last year, Mr. Kerik was indicted on 16 other counts by a federal grand jury 10 days ago, just before Ms. Regan let loose with her lawsuit. Whether Ms. Regan's charge about that unnamed Murdoch "senior executive" is true or not -- her lawyers have yet to reveal the evidence -- her overall message is plain. She knows a lot about Mr. Kerik, Mr. Giuliani and the Murdoch empire. And she could talk.

Boy, could she! As New Yorkers who have crossed her path or followed her in the tabloids know, Ms. Regan has an epic temper. My first encounter with her came more than a decade ago when she left me a record-breaking (in vitriol and decibel level) voice mail message about a column I'd written on one of her authors. It was a relief to encounter a more mellow Regan at a Midtown restaurant some years later. She cordially introduced me to her dinner companion, Mr. Kerik, whose post-9/11 autobiography, The Lost Son: A Life in Pursuit of Justice, was under contract at her HarperCollins imprint, ReganBooks.

What I didn't know then was that this married author and single editor were in pursuit of not just justice, but sex, too. Their love nest, we'd later learn, was an apartment adjacent to ground zero that had been initially set aside for rescue workers. Mr. Kerik believed his lover had every moral right to be there. As he tenderly explained in his acknowledgments in "The Lost Son" -- published before the revelation of their relationship -- there was "one hero who is missing" from his book's tribute to "courage and honor" and "her name is Judith Regan."

Few know more about Rudy than his perennial boon companion, Mr. Kerik. Perhaps during his romance with Ms. Regan he talked only of the finer points of memoir writing or about his theories of crime prevention or about his ideas for training the police in the Muslim world (an assignment he later received in Iraq and botched). But it is also plausible that this couple discussed everything Mr. Kerik witnessed at Mr. Giuliani's side before, during and after 9/11. Perhaps he even explained to her why the mayor insisted, disastrously, that his city's $61 million emergency command center be located in the World Trade Center despite the terrorist attack on the towers in 1993.