Newt Gingrich called President Obama "the most radical president in American history" at the Southern Republican Leadership Conference last week.

The leader of the 1994 Republican Revolution is a smart man and a historian, so he must know better. But he's also exploring a run for president, an action that frequently suspends good judgment in pursuit of sound bites. Perspective is the first thing abandoned in hyper-partisan attacks.

So here is a look at five presidents who, it could be argued, exceed Obama in the "radical" sweepstakes.

• Franklin D. Roosevelt
• John Adams
• Andrew Jackson