Who would he have picked as a running mate?
If he wanted to clamp down hard to win votes in the south, he could have chosen Howard Baker; moderate conservative, widely respected, and would ensure vote at least from the upper south. If, however, he was perceived as being too moderate (this depends on how he wins the nomination), he may choose conservative insurgents like Phil Crane or Paul Laxalt to 'balance' the ticket both regionally and ideologically. Outside of that, Jack Kemp would be a good, moderate conservative choice from New York, though his age may be made an issue (not that it destroyed Dan Quayle in '88; he did that for himself). There are undoubtedly other more moderate or more conservative choices, but those are the big ones; he would not pick anyone outside of a centre-right to right-range for fear of being perceived as a 'liberal'. He would also (perhaps; again it depends on the POD) has the fortune of not having to run against Anderson as well as Carter in the general election, which may help him out in some moderate northern states that Reagan won by a hair IOTL.