Election 2004 was the first national elections where the Internet was an integrated part of the election and used in every facet of this campaign.
The Palm Beach Post had a great editorial today "Now running: The Web" where the paper notes:
One of the starring roles in the 2004 campaign goes not to a candidate but to the Internet. A physician from a tiny state could stun the political Establishment and contend for a major-party presidential nomination because technology enabled him to go around the Establishment. He made online house calls, seeking money and support, from the wired world. Dr. Dean's issue was opposition to the war in Iraq, and he tapped into strong emotions. His audience may not have reflected the nation as a whole, since the wired world tends to be younger and single, but the Establishment got the idea. In particular, John Kerry and the Democrats raised lots of money in $50 online increments.