Valid points, with love to George. But there's a bit missing from that pithy take. The reasons you don't see enough "good politicians" are the same systemic reasons we say "all cops are bastards".

The carrots and sticks in the system are all lined up to weed out a certain kind of person, and to give another kind as much help as they need. The carrots I'm thinking of are campaign finance and the sticks are corporate media.

The American political system loves people who are cynical mercenaries, vituperative demogoues, or any alloy of those traits flexible enough to find a lasting niche. The exceptions prove the rule, to my mind.