First, citizens don’t vote for a representative simply based on who they judge as best matching their interests, but rather on who they judge as best matching their interests given the candidate’s chances of winning in the election.
Second, the successful candidate –the people’s elected representative – doesn’t simply vote for the policy that best matches his/her constituency’s interests, but rather for the policy that best matches the constituency’s interests given the chances of the policy winning in a legislative vote.
If both the people and their elected representatives followed the above strategy, social progress would be made, albeit not at the pace that anyone would find especially desirable yet that all could tolerate. To my mind, that is an optimal outcome for a democracy that respects the judgemental capacity of its individual members.
Note that in both steps, we’re talking about the voter or the representative functioning as a reflexive agent in his/her judgement. You might think of this as a ‘populist’ version of Fabian socialism — given that the original Fabians were technocrats — which works in a society that is at once smart and patient, two qualities normally seen as opposed to each other.