I'm pretty sure the "familiar foe" is Daniels. He was in a clip for the montage of the entire season very early on.
Also, I think the First Daughter is in on this. Nice little switch? Pretends to be scared and makes up with Mommy -- and she's in. (Dad getting shot was a lucky coincidence for her to get into the White House. Perhaps his "framing" was to accomplish the same thing, only he wasn't supposed to get hurt). Remember, she didn't like Mommy after she was punished for screwing around with the campaign.
Ethan is worried that the offspring will screw things up, but not because he's the mole. Although if the "foe" is who I think it is ...
Lots of possibilities here.
--Ted