Who cares? Obama was supposed to brilliant and look how that turned out?
Reagan was supposed to be a fool and is considered on the best of all time.
A lot of folks identify with leaders to whom they feel a connection. Reagan was a former actor, a talent that came in handy when addressing, Congressmen, the Media and the public. These qualities are much more important for a President to have than a high IQ is. People with high IQ's sometimes seem distant and aloof to others.
