FP colleague Tom Ricks wonders why CIA director David Petraeus had to resign in the wake of revelations that he had an extramarital affair with his biographer. In fact, the reason is quite straightforward, and independent of any questions about his judgment, or the security of his email account.
In the world of intelligence, extramarital dalliances are dangerous because they create the obvious potential for blackmail. If some foreign intel service found out that a mid-level intelligence analyst or operative was cheating, they might be able to extract sensitive information by threatening to disclose the indiscretion.
Obviously, if the director were caught in a similar indiscretion but remained in his post, it would send exactly the wrong message to the rest of the organization. Petraeus clearly understood that, which is why he was correct to submit his resignation.
One can take no pleasure from such a fall from grace, especially given that President Obama was reportedly happy with Petraeus' performance in a difficult job. But there's no real mystery why Petraeus felt he had to step down, or why Obama ultimately agreed.
Ricks also thinks the government's loss may be Princeton's gain, meaning that Petraeus might be in line for Princeton's presidency (soon to be vacant). I've got news for him: This is not the sort of publicity that university boards of trustees welcome.
Stephen M. Walt is the Robert and Renée Belfer professor of international relations at Harvard University.