“Looks like there are 9 states that have signed up for this, all solid democrat (of course).”
Not that it can be legally challenged right now, because it lacks the state to bring it into effect, but the national popular vote violates the Compact Clause of the Constitution that bars states from entering into compacts or treaties with one another.
Assuming Romney wins and gets to replace a liberal judge or two, expect the Supreme Court to strike it down if 270 EV worth of states ratify this. (I would have said expect the Supreme Court to strike it down, since it is so obviously unconstitutional but for John Roberts’s weird Obamacare decision.)