What is Political Philosophy?

What is political philosophy?  Where to begin?

"This volume provides an unequaled introduction to the thought of chief contributors to the Western tradition of political philosophy from classical Greek antiquity to the twentieth century. Written by specialists on the various philosophers, this third edition has been expanded significantly to include both new and revised essays." - The History of Political Philosophy

"There is no inquiry into the history of philosophy that is not at the same time a philosophical inquiry." - Leo Strauss

What is political philosophy?  This is as good a place to start as any.  (The Leo Strauss Center)