It's Mike, the secret service guy. It really can't be anyone else. The mole is inside the White House and someone they haven't investigated yet. Mike makes all the sense in the world, so many things have not been explained yet about him. Dude benefits from most of the SS getting blown up at the capital and he steps in and runs point for POTUS. Plus the dude seems to be in the loop on way too many top secret dealings, do SS really act as a consigliere for POTUS?
It would have made zero sense if it was Mike.
I thought it was the old guy, I think high up in cia, or something who was on the porch with the crazy rich speaker who wants to overthrow the government