Well, we do know Bush smoked weed. However I doubt it was a frequent thing, since he is flirting with fascism here, which is not pothead behavior.

But you're right, a pothead or ex-pothead probably could not make it to the presidency if people knew about it. Weed has had bad stereotypes associated with it ever since it was the drug of choice for the Mexican peasants and black jazz musicians in the 30s (thanks a lot Anslinger).

I suppose it doesn't really matter whether or not a weed smoker can become president. We all know the real path to social change is not through the ballot. We didn't vote the English monarchy away. We didn't vote slavery away. We didn't vote segregation away. We had to fight those things in the streets, and the same goes for drug prohibition and the plague of ignorance surrounding the issue of drugs.