3 USC § 19. Vacancy in offices of both President and Vice President; officers eligible to act.(a)
(1) If, by reason of death, resignation, removal from office, inability, or failure to qualify, there is neither a President nor Vice President to discharge the powers and duties of the office of President, then the Speaker of the House of Representatives shall, upon his resignation as Speaker and as Representative in Congress, act as President.
The 25th Amendment establishes the Presidential Line of Succession - who takes over if the President is somehow unable to fulfill his duties. Just in case, the Succession was established down to 18 positions meandering through some select congressional and cabinet positions. Good thing too, because now we need it.
President Jerome Young has just been implicated in a massive Saving and Loans Scandal, exposing corruption so deep that the President was find to be possibly involved with a couple murders - the President, several Senators, and the majority of the Cabinet. In fact, with the arrests and criminal activity being exposed the Secretary of Education Joshua Walters is now the Acting President of the United States - 16 spots down the line. Everyone above him either is under arrest awaiting trail or not a natural born citizen of the US, Joshua can honestly say he wasn't involved and is innocent.
It shows. With dozens of it's political leaders now proven to be wanton criminals, even murderers, confidence in the US - both domestic and abroad - is at an all time low. Joshua Walters, a man believed by many to be at best to naive for politics and at worst just someone who managed to keep the charges from sticking to him, is now being called up to the highest office to try to clean up the mess. As the first single president since the 1800's and the first atheist president ever, he's already got a lot of people against him.
And now he has to wonder if he just managed to steer clear of the corruption of President Young because he didn't have enough real power to tempt him, or it was just the wrong kind of scandals. Because they do say Power is the Ultimate Aphrodisiac...