Trumps pick had more to do with electoral college votes
than anything.
In addition to the strategic impact on the electoral college, there was a tactical reason for this pick. Pence is a solid GOP guy. I don’t mean GOP-e, because his conservative bona fides were there when he was in Congress. What I mean is that he is not considered an outsider by the GOP.
The tactical impact is that it will defuse the anti-Trump movement and kill it off even before the convention. This is a party unity pick.