> In what forum today are politicians given an opportunity to speak/write intellectually?

That quote is from a letter from Jefferson to Madison.

Barack Obama famously wrote a book. A "leader" leads by example. So I have a different take than your "sadly politicians are discouraged from thinking" and it goes like this:

Patronizing and conditioning the political discourse to be at the level of 'high school civics class' is a powerful mechanism for keeping actual thinkers away from politics.