The Speaker of the House of Representatives.
The Presidential Succession Act of 1947. This gives clear order to who would become president if the President and Vice President where to die or be incapacitated and unable to perform the duties of president.
President of the Senate and to be ready to serve as president in the event that the president becomes incapacitated or dies.
As far as the progression of power it goes President Vice President and the Speaker of the House of Representatives.
I think it may be the President pro tempore, as he is third in line if the President and the Vice President are killed or incapacitated.
The vice president can serve as the president in this case. Amendment 25 specifies procedures to be followed if the president says he is unable to serve and voluntarily yields his power and if he does not think he is incapacitated and how he can get his power back if he recovers his capacities.
First in line is the Vice-President.
The President is still the President if he or she is out of the country - it's only when he or she is INCAPACITATED that the Vice-President becomes (acting) President.
The Sec. of State is next in line.
If the President dies (or is permanently incapacitated), the Vice President succeeds to the Presidency for the remainder of the President's term. If there is sufficient time involved, a new Vice President will be nominated to serve the Vice President's term. If the President is alive but temporarily incapacitated, there is a complicated procedure for allowing the Vice President to act as Acting President temporarily, as spelled out in the 25th Amendment to the US Constitution. The amendment considers the cases where the President voluntarily yields his powers or when he does not, as well as the process of returning the powers to the President if he recovers.
If the Vice President was no longer there due to death, resignation, or becoming President, the acting President can appoint a Vice President. The new VP has to be confirmed by a majority vote o both the US Senate and House of Representatives.
Is a step above a vice president. Is next in charge to the president.
The Vice President of the United States has only two designated functions. He (or she) presides over sessions of the US Senate. And he (or she) becomes president or fills in temporarily if the President is killed or incapacitated. Beyond that, the Vice President does whatever the President wants, as long as it is legal.