A question that anyone representing a group whether appointed or elected is always do you enact the will of those you represent or do you owe those people your best judgment.
Usually the people in positions of power have spent more time thinking about an issue and listening to arguments than the average man on the street. For proof check out any news show man on the street interviews.
To vote against a populist opinion you need conviction, thought and a bit of ego, but I have more respect for someone with consistent convictions than someone who blows in the wind even if I disagree on a given issue.