"All those things they say about love being blind — well, it's true, love changes us chemically," says Katz, who counsels couples and families at New York's Ackerman Institute. "People get into complicated situations. The sad part is that when there's no one to talk to about it, you can really lose your way even more. The secrecy adds a whole level of confusion."

Still, says Katz, "it's his wife and his family who will ultimately decide if he is forgivable."

And, of course, his constituents. That's the bottom line, says Steven Cohen, professor of public administration at Columbia University. Sure, he acknowledges, "There was an intensity of feeling here. He was hardly Client 9," as Spitzer was famously referred to in court papers.

But, he says, "It's credibility more than anything else. The issue is whether a public official levels with his constituents. And disappearing for nearly a week is not leveling with your constituents."

Whether or not Sanford resigns or is forced out — he says he is hanging tough — it's his wife, Jenny, with whom he was long seen to have a strong, loving relationship, who faces the crucial decision of whether to forgive, as did Silda Wall Spitzer, Hillary Rodham Clinton, Elizabeth Edwards and others before her.

Jenny Sanford has not been shy about her shock or hurt. She has said that when her husband left most recently she had hoped he was off to soul-search, and was devastated to learn he was in Argentina.

For the wives, the "love factor" becomes especially painful and tricky, relationship experts say. Because while others may find some reason for sympathy, for a wife it's probably more painful to hear your husband fell in love than that he had a meaningless sexual dalliance.

"It's a fairly consistent finding in research: Women say anonymous sex would bother them less than an emotional connection would," says Coontz, the professor, who is also author of "Marriage: A History." She adds that men are more often bothered by the sex, because it threatens their manhood.

"All infidelities are wounding in different ways, and especially when they're magnified by public humiliation," says Coontz. "But if you've decided to work on it, it might be easier to deal with someone who's been blindsided by their emotions, rather than someone who has compartmentalized them, with that sense of entitlement, as in, 'the normal rules don't apply to me.'"

It's also perhaps slightly more comforting to know that one's spouse at least hasn't engaged in risky or deviant behavior, says Gail Saltz, a therapist in New York.