I disagree.
Kerry had been beaten down in the polls for over a month by the Swiftboat adds. The Republican convention bounce just made things worst.
The purpose of the memos was to put Bush on the defensive. The Democrats don't do well on the defensive. They needed something, anything, to switch the focus back unto Bush. The effort was only partically successful. It took the focus off of Kerry, but the focus has become Dan Rather/CBS, not President Bush.
The Damage control that is going on now at CBS is to make sure the fallout from the documents do not harm Kerry/DNC. CBS is not so concerned about their own reputation because they know their sponsors will not leave.
So, what if you knew that this was being planned by the DNC as far back as August 11 (prior to the SwiftVets getting much press). See:
http://www.freerepublic.com/focus/f-news/1216791/posts for confirmation that Bob Tuke, a Kerry supported from Tennessee, knew about the planned National Guard-missed physical-cocain story that was coming.