To make an extreme example, let's say that 99 senators are great and everyone loves them, but 1 senator is terrible and the rules of the Senate happen to allow

To make an extreme example, let's say that 99 senators are great and everyone loves them, but 1 senator is terrible and the rules of the Senate happen to allow filibusters. You could have a situation as a result where 98-99% of people approve of their senator, but a small minority approves of the overall output of the Senate.