Commander in Chief

First episode
While at an official ceremony with husband and Chief of Staff, Rod Calloway (Kyle Secor), Mackenzie is informed by the President's Chief of Staff, Jim Gardner (Harry Lennix), that President Bridges is about to undergo emergency brain surgery for a tumour. Mackenzie is stunned when Gardner tells her that in the event the President does not recover, the party doesn't want her to succeed him. Instead, she's asked to step down in order to allow the Speaker of the House Nathan Templeton (Donald Sutherland) to assume the post.

Bridges dies before transition plans are finalised, however, and Mackenzie decides to forge ahead and assume the presidency despite the obstacles that lie ahead.