Officially the Vice President is the person in charge of the Senate, but they are not a Senator. Patrick Leahy (D-VT) is the President pro tempore. When the Vice President cannot be in charge, the President pro tempore is in charge of the Senate. Many people still think of the President pro tempore as "de facto" president of the Senate. Benjamin Wade was only one vote away from becoming the President of the United States due to the impeachment of Andrew Johnson. No president pro tempore has taken over the presidency as of March 2020.