Slate contributor Mark Oppenheimer has a wonderful piece in this weekend's New York Times Magazine about Dan Savage, a longtime sex columnist for Seattle’s alt weekly the Stranger, and his theory of nonmonogamy. Oppenheimer explains Savage's take on monogamy in long-term relationships:

Savage believes monogamy is right for many couples. But he believes that our discourse about it, and about sexuality more generally, is dishonest. Some people need more than one partner, he writes, just as some people need flirting, others need to be whipped, others need lovers of both sexes. We can’t help our urges, and we should not lie to our partners about them.

This is a fairly sensible attitude—but as Oppenheimer points out, it's much more complicated in practice than in theory. While I agree with Savage's general stance, I think he's off-base when it comes to the impact of infidelity on political marriages. Savage wrote in an email message to Oppenheimer:

Folks on the verge of making those monogamous commitments...need to look at the wreckage around them—all those failed monogamous relationships out there (Schwarzenegger, Clinton, Vitter, whoever’s on the cover of US Magazine this week)—and have a conversation about what it’ll mean if one or the other partner should cheat. And agree, at the very least, to getting through it, to place a higher value on the relationship itself than on one component of it, sexual exclusivity.

But how are the Vitter and Clinton marriages "failed monogamous relationships"? Both the Vitters and the Clintons are still together, so either the couples in question had an agreement about having a non-monogamous marriage, or they were able to get beyond the fact that their partners strayed. In the case of Schwarzenegger, I would bet good money that Maria knew about Arnold's cheating heart before they got hitched. What spurred the divorce was the fact that he never told her about a child conceived with a domestic employee--right under her nose, in her own house. It was humiliation, in that circumstance, and outsize betrayal—not just the sex—that ended that marriage. Whoever is on the cover of Us Magazine is having his or her affair blared to the universe. I'd argue that's a lot more destabilizing than just sex.

Furthermore, there's some evidence that even if they don't talk about it beforehand, many individuals can forgive a partner who cheats. In a 2007 survey of more than 70,000 men and women by MSNBC.com/iVillage, only 19 percent of people who were cheated on ended a relationship right away, and 22 percent more said the relationship eventually ended because of the betrayal. That leaves 59 percent of people who stayed with someone after an affair was revealed.

So is it better, as Savage says, to have a conversation about nonmonogamy, or to try for monogamy and potentially fail? Which is more destabilizing to a marriage? If you're a public figure, it's probably better to have the talk first, so you don't find out about your husband's affair in People magazine. But in civilian relationships, I'm not so sure having the talk is worth it.