Bush must be up 5% over Kerry, since DemocRATS vote early and often.
5% is actually my comfort margin as well. If W is up by 5, then even if the RATs have registered thousands of voters who are not being counted in the polls, it still won't be enough for a Kerry win.
A 5% lead will also mean that W will win by big enough margins in the swing states that the RATs can't cheat and won't be able to credibly claim W didn't get a mandate. Winning by 5 will certainly not be easy, but we have a real shot at pulling it off.