I tend to agree with Patrick Ruffini that Gov. Sanford should not be obligated to resign for having an affair (as distinct from his disapperance and deception of his staff). While I think that resignation is a perfectly legitimate, even appropriate, path to take after disgracing oneself, a personal disgrace should not necessarily require resignation from one's job, whether in politics or the private sector.
Indeed, as I pointed out in the comments there, I've been trying to think of a prominent politician who resigned from their elected political office because of an affair (note: McGreevey and Spitzer resigned because of the major ethics/legal violations involved, not the affair), and the only one I can come up with is Rep. Livingston, who resigned his Congressional seat in 1999 after admitting an affair. I'm sure there are others - probably more at the State/local level - but I can't think of them offhand.
On the other hand, I have to disagree with part of what Max Borders wrote here.
The Right is now reaping what it sowed. By making social conservatism central to its platform, it left no room in the GOP for sinners.
I don't think the backlash against Gov. Sanford has a lot to do with social conservatism. Social conservatives do not have a unique position on adultery. Pretty much everybody considers it immoral. And the social conservative position on gay marriage (which Sanford shared) is not predicated on heterosexual people being uniquely faithful, either. The appropriate criticism is not so much hypocrisy as it is failure.
Ultimately, there are no political or ideological lessons to be drawn from Mark Sanford's affair. There are only human lessons.
I also think Max is wrong on a practical and logical level to conclude from this story that "it is time to purge the Right’s politics of social conservatism". As a libertarian, I certainly favor the harm principle over the offense principle - that is, I think politics should focus on addressing force and fraud instead of things which are merely unpleasant.
I believe that libertarianism is a very internally consistent way of marrying the personal and political spheres, but I actually don't think it works. Or rather, it's wonderful in theory, but human nature has not adopted that theory for any large, sustained social group in history.
For my part, I've come to believe that libertarianism is a personal moral philosophy, not a political philosophy. It describes how we ought to behave individually, but it does not give us practical advice for how we can resolve social disputes in a political system.
The political system requires accomodation. Libertarians can either disengage or they can find a way to work within a coalition. Unprincipled? Maybe. But so is everybody. That's human nature.
But there is one final, very important point: Social conservatism is basically a personal moral philosophy (or tendency), as well. As Hayek said of conservatism, "It is that by its very nature it cannot offer an alternative to the direction in which we are moving. It may succeed by its resistance to current tendencies in slowing down undesirable developments, but, since it does not indicate another direction, it cannot prevent their continuance. It has, for this reason, invariably been the fate of conservatism to be dragged along a path not of its own choosing. The tug of war between conservatives and progressives can only affect the speed, not the direction, of contemporary developments."
Social conservatives also need to accomodate libertarians. That does not mean they must minimize their objections to immorality, but it does mean they are going to have to accept fewer litmus tests and, if trends hold, a somewhat less decisive role within the Right's coalition.
Social conservatives and libertarians do have some common interests. The Right's coalition has worked best when they have focused on those common interests and left the rest to the social and personal spheres.