I agree with much of the economics in his post, though I would frame the points with a different kind of rhetoric. But I think Krugman is nonetheless wrong to oppose TPP. You will notice the word “China” does not appear in his argument. He closes with a question: “Why, exactly, should the Obama administration spend any political capital – alienating labor, disillusioning progressive activists – over such a deal?” The answer is simple: either this deal happens on American terms, or an alternative deal arises on Chinese terms without our participation. For rather significant foreign policy reasons we prefer the former, and the pragmatic side of President Obama understands this pretty well.
Addendum: Brad DeLong comments.