Polling data are close enough that even if most people aren't affected, the ones who are may be significant.
In fact following [link|http://www.electoral-vote.com/|http://www.electoral-vote.com/] in the last few days, it looks like there has been a big enough shift in the last few days to swing the election were it held now. I'm guessing that the memo issue is a significant part of that. (And the backlash is a bigger deal than the memos.)
Cheers,
Ben