If memory serves, the Kerry campaign isn't paying for any advertising this month. They don't have to - the 527s like MoveOn.Org have a lot of money and they have to spend it all before the 60 day block* begins. Kerry can save his money ($75 million in federal matching funds, IIRC) for the last 2 months of the campaign.

Kerry has not stopped campaigning since the DNC Convention. He and Edwards went on a long trainstop campaign tour after the convention and he spoke today at a VFW convention.

It just seems that his poll numbers rise when he isn't actively campaigning, such as when he went snowboarding after locking up the nomination during the primaries.

I read today that, defying tradition, Kerry will be actively campaigning during the RNC Convention. Traditionally, the other candidate doesn't campaign during the other party's convention. For example, Bush was down in Crawford, TX during the DNC Convention. I guess quaint things like traditions don't apply to Kerry, though. I'll see if I can find the link, if anyone is interested.