Misplaced Optimism?

Kevin Drum sees hope in news that while a poll shows 90% of Republicans approve of Bush's performance overall, 57% say they favor stem cell research. I, on the other hand, see this as evidence of one of our biggest (and to me most inexplicable) problems; that Bush remains personally popular among Republicans regardless of whether they support him on individual issues. As long as he has their overall support, why should he care whether they agree with him on any of the issues?