The relationship between Frank and Claire was rocky throughout the entirety of season three. Despite the fact that he was finally in the Oval Office, it was clear that there was tension between them and that she had perhaps imagined herself taking on a larger role in proceedings. This would all culminate in a dark and nasty scene which saw Frank make it clear that there was only President and one person in their relationship calling the shots. In some ways, you can see where Frank was coming from, especially after Claire steered him wrong so many times during season three. However, enough was enough for the First Lady, and she ended up leaving him in the closing seconds of the final episode. What a cliffhanger! This obviously leaves Frank in quite a mess as he finally begins to gain some momentum in holding onto his Presidency, but it's hard to imagine them not reuniting...
