High Quality Content by WIKIPEDIA articles! The Vice President of the United States is designated by the Constitution as, ex officio, President of the United States Senate. However, during a vacancy in the office (such as that caused by death, resignation or presidential succession), the President pro tempore of the United States Senate serves as the permanent President of the Senate. Until the ratification of the 25th Amendment to the United States Constitution, there was no mechanism to replace a Vice President until the next presidential election.