Pew Research Center: Are Candidate Web Sites Propaganda or News?: "We found that the online campaign is clearly a two-way conversation between candidate and voter and often even among voters themselves. The content on the sites focuses more on issues than the 'horse race' tactics that often interest the mainstream media. On the other hand, these sites are self-serving and lack traditional journalism's scrutiny, balance and ability to compare candidates against one another."
Like journalism ever had "scrutiny, balance, and ability to compare..."
Anyway, outside of that rant, what candidates are using was defined by the ClueTrain Manifesto years ago: marketing is a relationship.
And that is all that article marketing and autoresponder series are based on - building a relationship based on common interests and trust.
Too bad politics is short on that trust aspect right now...