John Stuart Mill, one of England's greatest philosophers, chided for calling the Tories "stupid", wrote:
"I never meant to say that the Conservatives are generally stupid. I meant to say that stupid people are generally conservative. I believe that is so obviously and universally admitted a principle that I hardly think any gentleman will deny it.
Suppose any party, in addition to whatever share it may possess of the ability of the community, has nearly the whole of its stupidity, that party must, by the law of the constitution, be the stupidest party; and I do not see why honourable gentlemen should see that position as at all offensive to them, for it ensures their being always an extremely powerful party . . . There is so much defence, solid force in sheer stupidity, that any body of able men with that force pressing behind them may ensure victory in many a struggle, and many a victory the Conservative party has gained through that power."
So there you have it...perhaps the leaders of any conservative (small 'c') party may well not be stupid, but vast numbers of their supporters are none too bright, as JSM suggested and as we often see here on AnswerBank.