I think Josh Marshall's headline says it all: "Just Go Be With Her!".  But there's more:

Mark Sanford says that at least he will "be able to die knowing I had met my soul mate,"… And if that's not enough, he says that for all the grief his affair has caused, that if the affair means he can never run for president (think the ship's sort of sailed on that one), that it will have been worth it.

That's sweet.  But you know, he's going to have to choose at some point.  Because he's already demonstrated that he can't handle his executive position as governor and a marriage and a mistress.  Yes, it seems that the marriage is over, but remember, it was temporarily over last month when he wafted away to Argentina and virtually abandoned his job.

Which again, is a sweet, perhaps even romantic choice.  But it doesn't sound like presidential material:

Of course, when you're a middle-aged man facing the collapse of your life's work and abandoning hope of being with the woman you call your 'soul mate' rational decision making or a clearly considered plan may be too much to expect. But it does seem like there are two guys here. One saying he wants to serve out his responsibility to his state and reconcile with his wife and another using the press to broadcast a free form love poem to the girlfriend in Argentina.

So he's got to make a decision.  And if he won't, I think the people of South Carolina will make it for him.

If she's worth it, then he should have no regret about stepping down.

But he's trying to cast himself in the vein of King David.  Nope.  He should try to emulate King Edward VIII, and get off the throne to be with the one he (supposedly) loves.