When US President Teddy Bridges dies in office, the Presidency passes to his Vice President. There's nothing unusual about that, except for the fact that the Vice President is a woman.
As the first female president of the United States, Mackenzie Spencer Allen finds herself up against people who think that she's not suited for the job, including her own political party.
The series premieres with the life of President Bridges hanging in the balance as he undergoes emergency surgery for a brain tumor. His Republican party is in a panic wanting the Vice President to step down immediately in case she needs to take over.
Favoured to be the next President instead is Nathan Templeton, The Speaker Of The House, whose political ambitions and ideologies have the full support of the Republican party.
President Bridges dies and just before Mac - as she's affectionately known to those close to her - is supposed to step down, she refuses, taking office as President independently.
As she runs the country fighting for the support of her party, facing the backstabbing and power struggles characteristic of politics she needs to balance the needs of her family too.
Her husband is trying to cope with being the first First Gentleman, her twin teenagers are rebelling and her six year old is discovering the world.
Together they move into the White House where Mac starts her pioneering that will change their lives forever as she strives to secure the trust of a nation.