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Ezra Klein on the blogopshere as political tool:

As for the feasibility of using blogs as a campaign tool (a question Mr. Kuffner punts to Jim Cappozzola for further exploration), it would certainly depend on the campaign. If used correctly, a campaign like Hart's could powerfully benefit from the blogging "constituency". However, blogs could have a much stronger effect on smaller level campaigns, particularly House and Statewide contests.

I don't see why this should be the case. There are still few enough blogs out there that you won't find many in any particular locality - nor do people really look to the internet for local news/info (obviously there are exceptions, especially on/near college campuses). It seems to me one of the main upsides of the blogpshere is the unprecedented national and even international connectivity it affords. I'm not suggesting that makes it an effective tool for a national campaign, but it's hard to see how a local campaign could make better use of it.