I think this ought to be a slogan for the Democrats to Use - by way of saying "I think the American People have largely concluded that the Bush Presidency Has Been a Failure both as a President and as CiC" and follow up with "Perhaps the American People Have Realized to Their Regret That Our Current President Was Not Competent for the Job We Elected Him To Do and is Still Not Competent Today"
   
Get the Competency Question Out Flat in the Open and Make the GOP own the Bush Presidency as their product! I know that bluntly putting it out there will spark all kinds of outrage from the right - but that is exactly the point.... We've had Seven Years of Incompetence - from 9/11 to Katrina and  all through Two Wars and the GOP wants us to Trust their Policies Still Today??
   
Where this ties into the current situation is that calling into question the competence issue it also has the potential to drag in the Question of McCain's basic fitness for the Office in that his choosing Palin as his running mate is manifestly a matter of putting political considerations over her Actual Fitness for the Office. I doubt if  several interviews out into the near future the majority of Americans will consider her "ready on day one" for the Highest Office - But it's up to US to plant the Question in their Heads.
  
No I don't think that Obama need fear a backlash over the Question either - He's been out there and answered all comers including now FOX and passed wihtout a hitch.
   
That's my take on it.