This discussion may contain spoilers!
For a man who basically set Lee's entire story in S1 into motion, we know next to nothing about him, aside from one conversation between Lee and Clem in the back of the drug store:
"The man you killed...was he one of the monsters?"
"Was he bad?"
"Yes he was."
Lee was apologetic about the murder itself, but not about the nature of the person he killed...which seems to suggest the senator must have been a real piece of work to send Lee into a rage. But that also begs the question of what Lee's wife could have seen in such a horrible human being. Did she sleep with him merely to spite Lee? Did she have a moment of weakness after fighting with Lee, and was drawn to the senator's good looks and power? Or is there something else we're missing?