No, it is not opinion dynamics. I, too, saw the same information this afternoon on Fox News. Bush 50----Kerry 45---Nader (No % shown.)
It is an Opinion Dynamics poll. The pdf on the Fox News website has the full details.
Fox News/Opinion Dynamics. Conducted October 27-28. 1400 registered voters, 1200 likely voters. The 50-45 lead is the likely voters result.