He's the company president, but his assistant is 'the (real) power behind the throne'.
In Shakespeare's play, Macbeth kills the king and 'ascends to the throne'.
He 'ascended the throne' [=became king] after the death of his father.
(..) House Targaryen is gone. Not a single person who shares your blood is alive to support you. Stannis Baratheon won't back you, either. His entire claim to the throne rests on the illegitimacy of yours. Not impossible, not enough. Lannister, Targaryen, Baratheon, Stark, Tyrell. (..)2015 TvShow: Game of Thrones Title: Hardhome Season: 5 Episode 8
(..) While you can still speak in complete sentences. Advise you on what? How to get what I want. The Iron Throne. Perhaps you should try wanting something else. If I want jokes, I'll get myself a proper fool. How many hundreds of thousands of lives (..)2015 TvShow: Game of Thrones Title: Hardhome Season: 5 Episode 8