That's not his style, as his MO is to be often wrong but never in doubt. However, he did go counter to type and picked Indiana governor Mike Pence as his running mate today. It won't help him too much with winning theocons, as he's urged a ceasefire in the culture war in the past and quickly caved to economic pressures when a state RFRA bill became too hot to handle last year. However, he's well liked in small-l libertarian circles and should add some gravitas to the ticket, having a beltway veteran; Pence was a congressman with a budget-hawk streak for a dozen years before getting elected governor in 2012.
The Hillary camp cranked the rhetorical heat to 11, casting Pence as the most extreme nominee in a generation. From a legislative standpoint, she has a case. My first response was to assume the generations were those of fruit flies, since Sarah Palin and Paul Ryan are pretty conservative. However, Pence had a 99 career ACU rating while Ryan has a 89.2. Looking at the Heritage Action card, Pence scored a 80% for their inaugural 2011-12 stretch, so he's more Tea Party/movement conservative than establishment.
This isn't a swing-state pick, for if Trump needs help winning Indiana, he's in major trouble nationwide. What Trump does need is to keep conservatives at home and not lose votes to Gary Johnson's Libertarian ticket or not voting at all as a protest. Nominating a small-l libertarian will minimize the folks pulling the Libertarian lever or writing in the Sweet Meteor of Death.
A sound pick. He's not not my first choice, but he was the best of the short-list (with Sessions, Christie and Gingrich being the most posited alternatives) rumored this summer. I'm torn between a pox-on-both-houses non-vote or getting an industrial-strength clothes-pin to hold my nose with and voting Trump