Some people would see the job of a politician as finding a group of people whose view reasonably-well match his own, and then--if elected by those people--putting his own view in office. Other people see the politicians' job as finding a group of people whose views are at least somewhat in line with his own, putting forth a collection of views in line with what the people want, and then--if elected--pushing those same views in office that he advocated prior to election.
Ideally, of course, the politician's views would match those of his constituents. In practice, though, that's unlikely to happen perfectly. As to what should happen when the politicians' and constituents' views don't perfectly coincide, I think there are sound arguments to be made both ways.
Lawyers, after all, are ethically and legally required to support their clients' positions regardless of what they think of them personally. That's their job. While some people might look upon dubiously the concept of politicians act like lawyers in that regard, I think the idea would have merit with one caveat: lawyers are required to be open about who their clients are.
Unfortunately, it seems today we often have the worst of both worlds--politicians advocate for positions based upon political expediency rather than belief, but feel little obligation to reveal on whose behalf they're really acting.
And then there's the Clinton and Romney types who will just tell everyone what they think the audience wants to hear, and then just do as they damned well please once elected.