The president.
The treasurer will up hold the position
The Vice President
The Vice President
yes
The President Pro-Tem presides over the Senate when the Vice-President is not there. The Vice-President barely attends Senate meetings anymore.
president pro tempore
The Vice President of the United States is the constitutional officer who presides over the Senate. The president pro tempore presides over the Senate if the VP is unavailable.
When the regular president of the Senate is absent, the president pro tempore typically assumes the role of acting president. The president pro tempore is usually a senior member of the majority party and is elected by the Senate. If both the president and the president pro tempore are unavailable, the Senate may also appoint a temporary presiding officer from among its members to fulfill the duties.
The House of Representatives can impeach the President. The Senate conducts the trial and the Chief Justice of the Supreme Court presides for the President.
The President pro tempore (Latin for "president for a time") typically presides in the Vice President's absence. The most senior senator of the majority party is customarily chosen to serve in this position. Like the Vice President, the President pro tempore does not normally preside over the Senate, but typically delegates the responsibility of presiding to junior senators of the majority party.
The Vice-president of the US serves as the President of the Senate, therefore he acts like a chairman would in running the meeting. If the vice-president is unavailable to perform these duties, one of the Senators is chosen from among themselves to be "President pro-tempore" of the Senate.
The senate holds all impeachment trials. If two thirds of the senate finds him guilty then the president will be removed from office. Only the House can impeach the President, not the entire Congress.