Every two years, each of the 100 senators gets 24 hours to select an office, starting with the most senior member and ending with the most junior. T he Senate has a system of tie-breakers to determine seniority. In order of precedence:
1) Former senators returning to the body after a hiatus, with length of previous service acting as a further tiebreaker.
2) Those who served in the House, with length of service acting as a further tiebreaker.
3) Former presidents of the United States.
4) Former vice presidents.
5) Former members of the president’s Cabinet.
6) Former governors, with state population serving as a further tiebreaker.
7) Final ties are broken by the population of the senator’s state.