What is the main responsibility of a U.S. Senator?

The main responsibility of a U.S. Senator is to represent all the people within their state. Senators are elected by the citizens of their respective states and are responsible for advocating on behalf of their constituents' interests and needs in the legislative process. This representation is crucial as Senators help to shape national policy, laws, and government initiatives that affect the lives of the people they serve. Through their role in the Senate, they participate in crafting legislation, influencing federal laws, and addressing issues pertinent to their state's residents.

While advising the President and interacting with foreign governments can be part of a Senator's responsibilities, their primary duty lies in representing their state’s populace and ensuring that their voices are heard in Congress. Serving in the military is not a responsibility of a Senator, as military service is separate from legislative duties.