It's really easy to understand people generally move in the direction of those they associate with so politicians like McCain and other RINO's who have spent years living in DC begin to think and act like liberals. They party with lobbyist and as DC elites begin to view themselves as aristocrats, wealthy leaders of the masses. Term limits and shorter times while congress is in session, they must return to home state offices when not in session.

Government is geared to keep people on welfare the same goes for politicians they also collect welfare only to a higher degree.