Exit polls are done during the day when more voters are those who don't work. Thats why they always skew Democrat. In 2000 the early exit polls had Bush being slaughtered in Florida and even losing Georgia (remember how long it took Dan Rather to call Georgia, and it ended up going to Bush by 55-45?). I remember being at the RNC that afternoon and people were ready to jump off the roof.
I think you may be on to something. Daytime polls count people who don't work.