I'm not going to blame Obamacare on Bush. That would be stupid. Obamacare is squarely the fault of Obama and any Democrats and RINOs foolish enough to jump on his bandwagon.
That said, the epic failure that was the Bush-Rove "compassionate conservatism" (aka Socialism cloaked in conservatism) certainly helped create the conditions under which Obama and the Democrats rose to power.
Regrettably, I believe Bush likened (and terribly misread) working with Democrats from the Texas legislature to working with establishment, DC Democrats when he rose to the White House.
In his heart, I believe he sought a convivial atmosphere for genuine bipartisan cooperation (which he became accustomed to in TX) and occasionally threw them a few bones (No Child Left Behind, bloated budgets), yet in the end, it bit him in the rear.
Moreover, as much as I like Dick Cheney, I believe the neo-cons did a great degree of disservice to his presidency and harm to the GOP. Despite that, all future maneuvering and corruption by Obama & Co. in the executive and legislative branches cannot be pinned on or attributed to President Bush and Karl Rove.