@ehBeth,
we will never know. I think its best. HEs an honorable guy and a family guy. He knows that his age is a handicap, his family life would be disrupted at a time (now) that he wants to (probably) devote to a foundation in his sons memory, and he and his wife will help in Beau's family.
I think hes already staked a new place in Delaware for his retirement home. So I dont think that he will miss the whole arena.
Besides, hes too open to be a good campaigner.