Final answer:
The size of the constituency for the Senate is the entire state's population because each state is represented by two senators, who are elected to serve six-year terms.
Step-by-step explanation:
The size of the constituency for the Senate is determined by the state which they represent. The United States Constitution mandates that each state is allowed two senators, regardless of the state's population size. As a result, senators represent the entire state, making for a very large and diverse constituent body, especially in larger states like California and Texas. The Seventeenth Amendment to the U.S. Constitution specifies that senators are elected by the people of each state for six-year terms. Given this structure, the senator's constituency could encompass millions, reflective of the entire state's population. Unlike the House of Representatives, where the constituency size is roughly 700,000 citizens per congressional district, a senator's constituency includes the entire state's population.