The obvious person would be Pence, and he'd have the best campaign manager of all time either officially or unofficially.
But if he were to retire after the second term as VP, id pick Matt Gaetz. 1) he is a young prodigy of Trump who would be more than happy to endorse and campaign for him.
Or Rand Paul, he'd be an amazing President and he, as well as Matt Gaetz, or Pence would be absolutely perfect after Trump.
But more outside the box. what about Kanye West. Wouldnt that be something if he ran, im not sure which side he'd run for.
Matt Gaetz is an idiot who has no problem handing out H1B visas by the millions. If that POS ever gets elected, say goodbye to America. Rand Paul already campaigned and his support was around 1%, so no.