Claire is different from Frank. Frank is a monster who craves nothing but power and serves no one but his own legacy. It is clear that Claire has always had a conscience, but that she was able to ignore it because in her mind, the greater good was achieving power. Now she sees that Frank is a terrible power hungry president, and she feels unfulfilled. She was always able to ignore her apprehensions by thinking of the ultimate goal, and how achieving power would make her life and her sacrifices worthwhile. Now that they have made it, she realizes that this is not what she hoped for. They are so weak that she cannot even take a stand on a issue such as freedom of speech. In her mind, she made a ton of sacrifices to get her and Frank to where they are, and it was for nothing. She gave up on having a family and an independent career. Instead she is now merely a trophy wife who must rely on her husband for favors. This was never what she wanted, even if she was stupid and naive for thinking otherwise or for hoping for more. She became disillusioned and snapped.
She is certainly not a good person. You can infer that the reason she married Frank in the first place was to achieve political power, which is shitty. But her actions are understandable and I am personally rooting for her to take down Frank. If at the end of the day she prevents a murderous tyrant from winning an election, she will be redeemed in my eyes. My issue is with people sympathising with Frank but hating on Claire. How does the fact that Claire is not "good" make her worse than Frank, who is a killer and a tyrant? Especially when Claire still has so much room for redemption, in contrast to Frank.
By the way, I think that an interesting analog to Claire is Jackie. They have both done some clearly fucked up shit in the pursuit of power, but at the end of the day cannot emotionally keep up with Frank's ruthlessness. They should be applauded, rather than lamented, for that. In fact all the women on the show are pretty awesome imo, including Dunbar. The only real certain bad guys have been men in power, who are generally sociopaths in this universe. There is a Feminism in Media 101 essay to be written here.
