You can read the whole thing, but Krugman sums it up with this:
What Texas shows is that a state offering cheap labor and, less important, weak regulation can attract jobs from other states. I believe that the appropriate response to this insight is “Well, duh.” The point is that arguing from this experience that depressing wages and dismantling regulation in America as a whole would create more jobs — which is, whatever Mr. Perry may say, what Perrynomics amounts to in practice — involves a fallacy of composition: every state can’t lure jobs away from every other state.
Maybe what Perry might do as president is — well, duh — try to attract foreign manufacturing to America with incentives at the federal level. Or maybe he’ll make it so more American companies find it makes sense to keep their operations in America rather than move them overseas. It’s not cheap labor that Texas offers, but competitive labor. And it’s not weak regulation that Texas offers, but smart regulation. A national economy based on those principles doesn’t sound so bad to me.