About that

Spoiler:
Their relationship was on the outs at the beginning of s3. Frank wasn't broken by power but just had some momentary weird frustration that isn't that explainable. Claire didn't get broken by power; instead she felt like she didn't have power. We weren't shown the struggle so much as we were told to assume it.

It would have been really cool if the writers had written a story about how power breaks you. I'm not convinced this story is that. Granted the writers didn't create any coherent theme, so that makes it a little more open to interpretation, I guess.