The populace is often ignorant and ill-informed (given the vast quantities of information people now have to pick through to find the unbiased facts, and how few people do so, I still think these are valid labels).

Theoretically, the politicians should have a knowledge/expert-base available to make decision that the ignorant lay person would err on out of ignorance. While they should take the desires and motivations of their constituency into account, it is also their responsibility to use their (theoretical) greater knowledge to make a better and more informed decision than your average grocer would make. In fact, I would say it is a failure of the politician to make a decision that appeases his constituency rather than helps them. Not to say that the desires of his constituents should not be considered. Just that I think it is a disservice to merely appease your "clients" than actually serve them.

But I'm going into a medical profession, so I might have an unrealistic point of view on the matter.