The first answer to this question is misleading. Obama graduated from Columbia University (an incredibly competitive ivy league school) at 212 out of over 3800 graduates. He didn't major in liberal arts (as if that is even a major); he majored in political science with a concentration in international relations. He then went on to Harvard Law school where he graduated Magna Cum Laude, the second highest graduate distinction.

McCain graduate from Annapolis ranked 894 out of 899 (fifth from the bottom of his class).

I agree that this is probably not a true indication of intelligence. It goes much more towards work ethic. Plenty of smart people nearly fail out of college due primarily to laziness or a sense of entitlement.