"Is Romney Overreacting to Bain Attacks?" - long but interesting read - by Nate Silver
http://fivethirtyeight.blogs.nytimes.com/2012/07/17/is-romney-overreacting-to-bain-attacks/#more-32185
"Mitt Romneys campaign has begun to push back against the notion that President Obamas critiques on his tenure at Bain Capital have damaged him. A memo released by Mr. Romneys pollster, Neil Newhouse, suggests that the margin between Mr. Romney and Mr. Obama has been narrowing rather than widening in the polls despite the attacks.
I would take issue with the notion that the race has been tightening. Instead, once you remove the statistical noise from the polls, the trajectory looks roughly flat based on our analysis. Mr. Obama has maintained a narrow, but fairly consistent, lead of about 2 points over perhaps the last six to eight weeks.
But Mr. Obamas lead has also not been widening and I think Mr. Newhouse is correct that the evidence for the impact of the Bain attacks is rather thin, or at least has been up to this point.
At the same time, Mr. Romneys campaign has begun to behave as though the attacks are a fairly big deal. And it has backed into a more defensive posture that could change the nature of how they are perceived by the public going forward."
snip
much, much more - kind of wonkish, but worth reading....lots of detail/speculation just for consideration.