no one
The vice president duhhh!
the vice presedent
speaker of the house
The Speaker of the House becomes president if something happened to the president and vice president.
the speaker of the house
Next in line is Speaker of the House.
The Chief of Staff is a position appointed by the President. If the elected President and Vice-President are unable to serve, the Speaker of the House of Representatives becomes President and selects a Chief of Staff.
The Vice President serves the people and the President. When necessary he may vote in the Senate to break a tie vote.
First would be to succeeded the President if he becomes unable to serve out his term. Also serves as president of the senate, he may vote if a tie breaker needs to be broken
In the US there is a line of succession should a president be unable to serve due to illness or death. The next in line to serve as president is the Vice President. This was seen when President Nixon resigned and Vice president Ford became president. Should a vice president be unable to serve, then the Speaker of the House of Representatives becomes the new president.
The vice president serves as president of the senate. There are 100 Senators, and if there is ever a tie in the senate, the vice president gets to cast the winning vote. If the vice president is not available, somebody else will serve, he is called the president pro tempore.
If both the President and the Vice President are unable to serve, then the Speaker of the U.S. House of Representatives would become President.