Dear American100,
Although 38% of their sample was Republican, and 31% of their sample was Democrat, I think it's likely they weighted Republicans and Democrats differently in coming to their final numbers. Here is a link to a post I made on another thread examining this question:
http://www.freerepublic.com/focus/f-news/1207324/posts?page=255#255
The raw numbers would have gone 54% for Bush, 40% for Kerry if they'd have computed the poll without doing any weighting.
sitetest
Excellent analysis.
It jives with Bush being up 16 after his speech.