Brown’s race might actually end in triumph, rather than a close defeat. But win or lose, he’s demonstrated there’s no necessary connection between online organizing and liberal politics. The Web is just like every pre-Internet political arena: ideology matters less than the level of anger at the incumbent party, and the level of enthusiasm an insurgent candidate can generate.

It’s like other arenas, too, in its capacity to disappoint idealists. Indeed, it may be crueler to dreamers, because it offers an artificial sense of intimacy with politicians, without delivering any practical results. You can be Sarah Palin’s pal on Facebook, or have Barack Obama’s running-mate selection text-messaged to your cellphone. But Washington is still Washington, the legislative process is still the legislative process, and the power of an online community matters less than the power of the powerful…

If liberals are feeling disillusioned, though, their right-wing imitators may be ripe for an even greater letdown. The Obama administration has at least gone some distance toward enacting an agenda that the net-roots left supports. The “right roots” activists are rallying around politicians who are promising to shrink government without offering any plausible sketch of how to do it. When Scott Brown pledges an across-the-board tax cut and sweeping deficit reduction all at once, he’s setting the conservative grass roots up for a major disappointment.