Trump helped himself by helping Bush, who could be knocked out by a poor South Carolina performance. That said, I don't think it's some brilliant strategic maneuver by Trump. I think Trump is more of an instant gratification candidate who tries to look strong by attacking the weakest, most vulnerable member of the establishment herd, but in doing so, might get lucky, by driving mainstreamers to rally to W's defense which will leverage his campaigning for Jeb next week and give him a shot at topping Kasich and Rubio. I think Trump bumbled his way to a smart strategy.
Folks will vote for Jeb for the sole reason they thought Trump went too far in embracing left wing kookery about Dubya, so they will vote for Jeb to affirm Dubya?