She Has Been Number 2 for Far too Long.

Claire has been passed over again and again for far too long, and she is not the type of person to take all of it lying down. She has been continually denied positions and accused of only getting where she is because of her relation to Frank. She is, and always has been, simply an accessory to his public life, his Presidency, and his campaign. Claire Underwood is not the type of woman to sit back and enjoy being number 2 for her entire life. Frank tells her it’s always been this way, and that she’s always known this, but something seems to have snapped. Perhaps she doesn’t believe Frank can become president anymore, or perhaps she just can no longer stand the idea of only ever being number 2. Either way, she has abandoned Frank, and will no doubt find another more efficient route to greatness, most likely her own campaign, or possibly joining Heather Dunbar on the ticket.

Claire has Spent Some Strategic Time in the Spotlight

Claire has already been quite popular (and unpopular) with the nation over her abortion and affair scandals. She’s been featured on many news channels and been interviewed several times. However, no publicity is bad publicity. Claire’s name is now out there — and people know her. All she has to do is get those who support her to continue to support her, and get those who don’t, to keep talking about her. She seems to be reveling in the spotlight and building her popularity and name to possibly use in a future campaign. After all, Donald Trump has been getting a lot of hate, but is still doing quite well for himself.

“Its you that’s not enough”

At the end of a Season full of twists and turns, of disaster and recovery, Claire ultimately stands up to Frank. She says to him, “It’s you that’s not enough.” We as viewers assume she’s talking about him in the sense of their marriage — that Frank is no longer “man” enough or able to support Claire emotionally and sexually. However, it could be that the writers decided to include a third layer in this line — a layer insinuating that Frank Underwood does not have what it takes to be President of the United States. Is Claire suggesting something that she knows about the future, that Frank doesn’t?

Claire is Ruthless

Claire is Ruthless. We've seen her do things that would make a lot of our stomachs turn. We've seen her do things for power, to help Frank get to the presidency, that would be unfathomable for most wives. She condoned the murder of Zoe Barnes and she condoned the manipulation of most of Washington. No one would put it past her to run against her own husband. In fact, after being pushed down for so long by him, he is the exact person she would want to lash out at the moment she decided to abandon him and his plan to the White House.

“Heather Dunbar Won’t Win Because She Doesn’t Have Claire Underwood By Her Side!"

Frank himself says that he will win because Claire Underwood is standing by his side. Does this mean that Heather Dunbar would win if Claire were standing by her side? Is he trying to say the only way he can win is because of Claire standing by his side? This may simply be Frank pandering to the audience, but it may also be the writers foreshadowing something a possible loss in the future. Well, Claire is no longer by Frank’s side. Is Claire going to join Dunbar’s ticket? Is she going to run herself?

Claire Sitting in the Oval Office

This is perhaps the strongest case for Claire’s presidential campaign. She is already imagining herself as the President! Frank walks into his own office to see someone sitting in his chair — his own wife. The way Claire faces Frank, an inexperienced viewer could mistake Frank as the First Gentleman and Claire as the President. She fits the chair so naturally and elegantly that it is almost impossible to imagine Claire NOT running for President. This is some of the more blatant foreshadowing done by the writers, and we’ve certainly picked up on it.