I know he is. I also know he's got a ton of money and a comfortable lead in the polls. Let's face it. Jeb's quite the powerful political figure in his own right and will run a strong race. But some of the candidates trying to knock off incumbents nationwide (Taylor in MT, Simon in CA, Talent in MO) would benefit even more from the President's help, and our nation (IMHO) would benefit even more from winning a few of those races rather than increasing Jeb's margin of victory.
(I realize Dubya is doing and has done many other fundraisers, including for Simon.)
He'll do that. It looks like the "new tone" BS is disappearing to an extent, which is good.