I believed that when my grade school teacher said it.
I believe it is still true for city and county positions. You don't get to be President, though, by wanting it bad enough. It takes millions of dollars, licking lots of boots, and basically being a sell-out. Same with Congress. If the FedGov had less power, what you say would be closer to truth. Unfortunately, the size of government raises the stakes to a point where you don't rise from "regular joe" to be Nancy Pelosi, Harry Reid, or Barack Obama.
Those people are not like me, and they're not like you. They are part of a different caste. They just don't have special paint on their foreheads.