I think McCain will reach out to Conservatives. Pragmatically he needs support as and only one side will give him that so he has no choice. Once in office who wants to be an automatic lame duck? Even McCrazy will want a legacy....they all do (well maybe all but Ford). Look at how much Bill has it on the line for Hill because he knows he doesn’t have a good legacy and wants a second chance.
McCain has already sworn (repeatedly) that he would hold only one term (same promise he made back in 2000).
How much credibility, and trust you have in him is up to you, but legacy is not part of the picture if he is telling the truth about his plans, if he really wants to follow through on Bob Doles Promise (in 1996, he also promised only one term if elected), then the VP candidate becomes the major consideration, and I don't trust McCain nor know who he would choose as his VP.