The role of the president pro tempore of the senate is to preside over the chamber in the absence of the President of the Senate, who is also the Vice President of the US. Unlike the President of the Senate, who is not an elected member and can only cast a vote to approve legislation when there is a tie, the President pro tempore is a senator elected by the members and is able to speak and vote on any legislation and to appoint various congressional officers as well as other positions.. Furthermore, he or she is also the third in the line of presidential succession, following the vice president and the speaker.