As Jason notes, while the blogosphere may have provided much of the necessary skepticism toward the evolving explanations of Mark Sanford's several-day absence, it's unlikely the story of his affair would have broken (at least any time soon), had The State newspaper not received a few anonymous tips--specifically, a few romantic emails provided to the paper last December, and word that Sanford would be arriving at the Atlanta airport on a plane from Argentina yesterday morning.
Both of these tips seem as though they could only have come from an awfully small universe of possible sources: someone in Sanford's family (his wife's statement suggests she is, understandably, still furious), someone in his office, or, conceivably, the other woman herself. Who it was, and whether he or she intends to follow up with any further revelations, could help determine whether Sanford has any political future left at all.
--Christopher Orr