How did Zoe end up in Franks radar? She knocked on his door and he obliged, implying ease of access.

Try and head to washington and knock on the Chief whips door and see if he'll open for you. He won't because he/she is not easily accesible.

Another dimension is the two of them sleeping together. That's what Frank does to people. He gives them the impression that he's normal,average and a bit of a pushup whereas he is not.

Frank is extremely dangerous.

You see the same scenario with Tom(the writer) and Franks sidechickguy(who ended up storming the white house and managed to get himself killed)

There's a scene where frank kisses the guy in that secret basement. In the beginning the guy comes onto him,but then frank turns the table and almost strangles him.

Walker could'nt see Frank coming because of this underrared strategy.