Jeb Bush suffers from an obvious difficulty: American dislike of dynasties. Possibly there is some way to get around this problem, because he would be a great president. W. was better than his father, and Jeb would be better than W. But yoking him with McCain would permanently wreck any slim chance of a presidential future he might have. It's a terrible idea, any way you look at it.
If McCain does what Bush's father did and raises taxes, probably. The resulting downturn would sweep the Dems in in 2012 on a "worst economy in 50 years" campaign, whether Bush or McCain was the nominee. In other words 1992 all over again. If Bush ran in 2012 or 2016, he would be forced to defend the tax increase in the GOP primaries and general election, or sound lame attacking the policy.