<P> The president pro tempore of the United States Senate ( / ˌproʊ ˈtɛmpəriː / or / ˌproʊ ˈtɛmpəreɪ / ) , also president pro tem , is the second - highest - ranking official of the United States Senate . Article One , Section Three of the United States Constitution provides that the Vice President of the United States is , despite not being a senator , the President of the Senate , and mandates that the Senate must choose a president pro tempore to act in the Vice President 's absence . Unlike the vice president , the president pro tempore is an elected member of the Senate , able to speak or vote on any issue . Selected by the Senate at large , the president pro tempore has enjoyed many privileges and some limited powers . During the vice president 's absence , the president pro tempore is empowered to preside over Senate sessions . In practice , neither the vice president nor the president pro tempore usually presides ; instead , the duty of presiding officer is rotated among junior senators of the majority party to give them experience in parliamentary procedure . </P>
what is the role of the president pro tempore of the senate
to act in the Vice President 's absence