We are safe in assuming that Mike Pence isn’t sincerely a Trump guy:
It's disorienting to have had commiserated w/someone re: Trump – about how he was unacceptable, & then to see that someone become Trump's VP
— Dan Senor (@dansenor) July 15, 2016
So what is he thinking? It seems simple: He just went from having some significant chance of losing his governor’s race to having some significant chance of being the next Vice President. That’s a pretty big swing to the upside. He also must figure that even if Trump loses, he may be ahead of the game for 2020 as a former vice presidential candidate compared even to a sitting governor of Indiana. So it is all upside. This is where he is probably mistaken. Even assuming no debacle while he’s on the ticket, being the #2 on a losing presidential ticket is not a great career enhancer (see Joe Lieberman, for example) and the transparent insincerity of Pence’s Trumpism presumably won’t be helpful to his reputation.