One reason for this lies in the nature of politics. Many political problems are either insoluble, or have quite simple solutions which are unsellable (basic income, voluntary jobs guarantee, drug legalization). For the former category intelligence is useless, for the latter unnecessary. But there's another reason. It's that intelligence (in the narrow sense of IQ or book-learning) can crowd out other virtues. For example:
- - If you're so brilliant you can pick things up quickly, you'll not develop the determination and stickability you need to cosy up to dullards, sit through interminable meetings or plough through red boxes.
- - Intellectuals want to say something interesting. And this leads them into "gaffes". Keith Joseph's flirtation with eugenics is the most notorious British example of this, but Larry Summers has made a career of it.
- - Intellectuals are, very often, out of touch; they might well therefore lack the political antennae which tells them what'll sell and what won't.
- - Intelligence can lead to one of two possible drawbacks. Sometimes, it can breed indecisiveness, which might have been Wilson's problem; being able to see both sides of a problem can rule out clear and decisive leadership. At other times, it might lead to overconfidence and hubris. The poll tax, remember, was the idea of intelligent people.
- More Here