Congress should repeal it, but they won't because those with actual political power like it.
That is the voters' problem. If they don't vote for a congress that will repeal the DMCA, it simply won't happen. Pretty basic, don't you think?
Actually, there are a couple of intermediate steps missing here.
The first thing you have to do is know who your Senators and Congressman (Congresswoman? Congressperson?) are. ("Do you know?" he asks, rhetorically, to the reader...)
And then, the second thing you do is to sit down and have a talk with them...and tell them your views on the matter. Don't come across like a fanatic or a crackpot; It doesn't matter how wrong you think the DMCA is, nor does it matter how strongly you feel it. What matters is *why* it's bad, in the frame of a logical argument. Facts and other such dispassionate information are what you want to have backing you up here.
Once enough people do those two things, it'll be enough of an issue that you'll actually be able to tell where a candidate stands on the matter. As it is today, I doubt very much that it'd be possible to figure out the stances of 90% of people on Capitol Hill without having to ask them directly, when it comes to this. The other 10% would be those who have spoken out...but 10% isn't enough to swing the issue at the voting booth.