The digital divide will ultimately determine how effective political blogs are at changing politics in the real world. Who can access the Internet to interact with opinion on blogs?
The "rallying the base" phenomenon may be the most important way blogs affect voter turn-out. Blogs are free to anyone with an internet connection, and such technologies can link the populace to the candidates through forums. It's likely that more people can surf the web on their own time than get to a political rally.
While Blogs allow virtually anyone, an El Salvador refugee for example, to publish their thoughts, political interest isn't tecnology driven. Reading the newspaper, having a stake in the issues, having politically active friends, being able to afford access to information (via Web or TV), weighs at least as heavy as Blogs in getting voters get involved.