Answer:
When dealing with a certain bill, the congressmen must fundamentally represent the opinions of the citizenry, since it is the latter who they represent: both Representatives and Senators represent the citizens of the Nation, being the Representatives the spokespersons of the will of a certain Congressional District, while the Senators are with respect to a specific State. But in both cases, they are due to the people who vote them and appoint them to their positions, with which, beyond their personal or party convictions, they should abide by the popular will when deciding their votes.
