The other day, somebody suggested that the capture of bin Laden has been Obama's silent ace in the hole. Though it hasn't been a front-row feature of the campaign, it gives him a huge edge in terms of pure public sentiment. I think Obama had a similar advantage over Hillary: It wasn't her fault, of course, but I believe that subconsciously, a lot of voters were turned off by the prospect of a Bush-Clinton-Bush-Clinton-(Jeb?) Bush progression.
In the same vein, I believe that though Seamus and the tax returns are "ancient history" as far as the MSM is concerned, those two insights into Mitt are still burning brightly in the psyches of the voters (if only because his subsequent behavior has reinforced them). And for Mitt to suggest that harping on them are a waste of time when it's "issues" that should be discussed, well, the quality of one's personal character is very much a political issue. Just ask Bush. And Clinton. And Bush. And Clinton. And (Jeb) Bush.