Answer:
The President pro tempore of the Senate is the second most important position of the Senate and the highest position as senator. According to the United States Constitution, the Vice President is also the President of the Senate, although he is not elected as a senator, so the President pro tempore leads the legislative body in practice. Usually, the individual elected to the position is the senior senator of the majority party in the Senate.
Neither the Vice President nor the President pro tempore presides over the Senate; in his place, this position is usually delegated to another senator of the majority party in the Senate. The President pro Tempore, after the Speaker of the United States House of Representatives, is the third person in the presidential succession line.
The current President pro Tempore of the Senate is Chuck Grassley, elected by the Iowa Republican Party