McCain won't continue Bush's legacy. He'll betray it
Bush won't endorse him.
McCain won't make it past New Hampshire, if he even runs. He is the candidate of the old media and his support doesn't extend beyond the studios of NBC, CBS, ABC and CNN (oh, and the NYT and WaPo editorial meetings) and a few gullible and easily led sheeple.
Bush almost certainly will refrain from endorsing anyone until after the nomination is in hand because he has class and honor, unlike the last few Democrats to hold the office. However, if he were to endorse anyone it is most likely a governor or former governor, probably either George Allen or, if things work out just right, Jeb.
OMG, NO! We can't afford another Bush in the White House. Jeb is a globalist just like Bush one and two!