This is an old topic in the political philosophy of representative democracies: is a representative supposed to just do whatever the most popular sentiment is?

This is an old topic in the political philosophy of representative democracies: is a representative supposed to just do whatever the most popular sentiment is? Or are they supposed to use their best judgement—given they, presumably, spend more time looking into and thinking about various issues, and have access to better experts and advisors than most members of the general public—even when that's sharply counter to public sentiment? Somewhere in between? Where does the line fall?