The correct answer is president pro tempore.
A member of the Senate majority party who fills a role that parallels the Speaker of the House is "president pro tempore."
In the absence of the vice president, the pro tempore is the officer of the Senate that is recognized by the Constitution to preside over the chamber. Pro tempore stands for "a time," so it means "president for a time," in substitution of the vice president. This figure in the Senate fills a role that parallels the Speaker of the House.