Why aren't smart people elected?

Instead of relying on charisma, why not have Presidents based on intelligence and knowledge?  Someone who has a masters or professional degrees, has written papers and books, and is just a really knowledgeable guy?  Rather than, um, someone who's not.

The brightest people (your professors, researchers, writers, etc) can't be bothered. They became like they are through the pursuit of their passion. Why would they go into politics?

"I just finished a series of studies in molecular biology that have determined the chemical folding of specific selenoprotein enzymes may be the key to curing certain types of hepatocellular carcinomas. What should I do now? Oh, I know! Become a politician so my opponents can smear me when they find out I've been fucking a couple of my post-doc lab assistants..."

Which brings us to politicians. Most of them are not stupid - which is why they pander to the masses like they do. If you want better leadership you'll need a more intelligent populace (who give a damn).