Who fills in for the President of the Senate when necessary?

The President Pro Tempore serves as the person who fills in for the President of the Senate when necessary, particularly when the Vice President, who is the official President of the Senate, is unavailable. This position is traditionally held by the senior member of the majority party and is primarily a ceremonial role, though the President Pro Tempore does have specific responsibilities, including presiding over the Senate during sessions and signing legislation. This role exemplifies the structure of the Senate, where leadership is clearly defined, ensuring that there is always someone available to maintain order and conduct Senate business in the absence of the Vice President. The other roles mentioned, while important within the legislative process, do not have the specific responsibility of presiding over the Senate when the President of the Senate is not present.