THE INEVITABILITY OF ANACHRONISM. I wholly endorse Ezra's argument here, and also strongly recommend Sandy Levinson's book (although, as is often the case, his diagnosis is more convincing than his remedies.) Obviously, to defend an institutional feature as irrational and undemocratic as the electoral college (even though it produced a constitutional crisis in the third presidential election after the Constitution's ratification!) merely because the framers designed it is ridiculous. To add another point, the reviewer Ezra cites claims that the Constitution is a "workable document that only got us through a bit under 250 years." The rather obvious problem with this is that the first Constitution failed, as it proved unable to prevent the collapse of the nation into an exceptionally bloody civil war. This is not because the framers were stupid, but because even very smart people aren't clairvoyant. One would think that this would have permanently made a stance of uncritical reverence towards the document untenable, but apparently not.
One other point about constitutionalism: I don't agree with Matt that if we could re-write the 2nd Amendment today it would be significantly less ambiguous. Ambiguity is a crucial constitutional tool, precisely because 1) constitutions have to create political communities among people with fundamentally different views, and
2) the future is unforeseeable, making some play in the joints desirable. A more specific Commerce Clause, for example, would make the Constitution completely unworkable in the 20th century, and among the most obvious constitutional blunders are historically bound clauses that are destined to become almost immediately obsolete (such as the clause in the Seventh Amendment guaranteeing a jury in a civil trial in cases where "value in controversy shall exceed twenty dollars.")