Is it Zogby who doesn’t poll over weekends because he says you can’t get a good sample?
I don’t know which pollster doesn’t, but I can tell you weekend polling is a proven issue. You get completely different results over weekends than during the week.
Look at Rasmussen, generally every monday you will see Obama usually slightly higher than he was on Friday, only to drop again on monday and tuesday as the weekend polling rolls out of the 3 day.