The conflict is to manage the interests of their constituencies to the detriment of the common good, that is, of all the citizens of the country.
Federal congressmen are elected in their states, but have the function of representing the entire country. In this context, there is a dual function. At the same time that they wants to guarantee improvements for their electoral bases, the congressman needs to take into account all citizens of the country. This is particularly important given the difference that exists between the states of the country.
The ethical standard suggests that the common good is the most important, and the congressman must value everyone, not just those in his state, who already have representative houses at the state level.