Who's in line for the presidency?
The order of succession is vice president; if the vice presidency is simultaneously vacant, or if the vice president is also incapacitated, the powers and duties of the presidency pass to the speaker of the House of Representatives, president pro tempore of the Senate, and then Cabinet secretaries.
If the President is unable to serve, the Vice President is next in line of succession. If the Vice President is unable to serve, the Speaker of the House of Representatives is next in line of succession. If the Speaker is unable to serve, then the President Pro Temp of the Senate is next in line.