This actually serves the Reps better than the Dems - it ties up the news distracting them from reporting the real issues in the campaign by sending them on a witch hunt. Additionally, it makes the Dems look like cheaters. If the documents are genuine (which you will never prove) it doesn't matter. If they are fake, it give Reps the high ground.

If Rove did this, its a very good dirty trick as it delays the discovery of the truth about Bush's service (not that most people haven't made up their minds already on this) and muzzles the Dems message.