The Chief Deputy Whip is the primary assistant to the whip, who is the chief vote counter for his or her party. The current chief deputy majority whip is Republican Patrick McHenry. Within the House Republican Conference, the chief deputy whip is the highest appointed position and often a launching pad for future positions in the House Leadership. The House Democratic Conference has multiple chief deputy whips, led by a Senior Chief Deputy Whip, which is the highest appointed position within the House Democratic Caucus. The current senior chief deputy minority whip, John Lewis, has held his post since 1991.

Answer this question, if possible (if impossible, reply "unanswerable"): Who is the Senior Chief Deputy Whip the assistant to?
unanswerable