The vice president becomes President if the President dies or is removed from office . There are also procedures by which the vice-president can temporarily assume the duties of president, either voluntarily or involuntarily.
Even though the question is who takes over the v.p. and not what the president pro tempore takes over
The Pro Tempore Currently, Robert C. Byrd
In a play the understudy takes over when the actor is absent for any reason. For example, when the actor is ill.
the President pro tempore
The 'President Pro Tempore' is the President of the Senate, when the Vice President of the United States is absent.
The Vice President. If the Vice President is absent, the Secretary runs the meeting.
The speaker of the house takes over(:
The Vice President
The vice president
Then the vice president takes over
The vice president
Speaker of The House