The books have been out for quite a while. Allen's campaign site isn't mentioning this, either, in the press release section.
If spun correctly, it could possibly be an issue, but it's not groundbreaking since it's been "out there" for so long, it my end up looking like a hail mary play to bury Webb once and for all, even though it's not really needed judging by the polls. Hopefully it won't backfire.
All it will do is boost Webb*s book sales as the perverts rush out to buy them:-)