None of your above candidates will be the next PM. Ukip voters have already decided this too. It will - of course - be the one who protests the most clearly and convincingly that (s)he holds no such ambition; has undying loyalty to the incumbent, and firmly believes they should continue forever.
So, you want a musical clue? Well.. this could be just about anything, because the clue is actually the format.
P.S. It is of course (according to The Guardian) "the joke candidate" - though not the one the substitute-for-thought Leftie Labelers like to dub The Buffoon Candidate.