My first post, and on a subject that I know a fair bit about from real life. It would not have been possible to declare for the presidency that late for the 2004 cycle because of (a) delegate slating and candidate filing requirements and (b) the fact that the Iowa caucuses were on January 15 and require more organizational work than just showing up.
As an example, the filing deadline for the New Hamshire primary was November 21 and there were a number of other filing deadlines for petitions that fell in early January and required a great deal of effort due to complex election laws (OH, NY and IL are examples).
Moreover, by December, Dean had locked up some big name endorsements (i.e. Gore).
It's a great idea and thoruoghly plausible, but the start date needs to be pushed back to reflect the realities of setting up a presidential campaign. If you need help with the actual filing deadlines, send me a PM and I can provide them to you, as I worked the 2004 cycle and have all of the data at hand.