I can certainly see the merit in this suggestion, but I wonder how fast it would run afoul of campaign finance reform laws. In my view, those are a far bigger impediment to citizen participation than this copyright issue. It’s always been morbidly funny that the political factions who want to “take politics away from the monied interests” have worked hard on a system that makes individual participation — except for money — very difficult. Of course, you can join a PAC or a political party, but on your own, as just a citizen? No way! That might be an unauthorized coordinated contribution to a candidate! And of course, the prohibition on naming candidates in advertisements during the black out period is just wrong, so it would be illegal for a citizen to put out such an advertisement, regardless of what source material to which he has access.
I think the blogosphere should keep an eye out for the first private citizen prosecuted for political speech under McCain-Feingold and publicize the heck out of it. I think the sight of a citizen being fined and jailed for making his own political advertisements might not go over so well with the citizenry.