This is the case, recently heard by the Supreme Court, that may place some First Amendment limits on McCain-Feingold's speech-suppression laws. The amicus brief in which the Independence Institute participated is here. A collection of other briefs and documents is here. It is a good test case because the advertisement in question (urging Wisconsin citizens to tell Senator Feingold stop supporting the filibusters of Bush-nominated judges) was plainly a communication about the business of Congress, rather than a thinly-disguised campaign advertisement (e.g., "Tell Senator Snort that you're upset that he was arrested for domestic violence 10 years ago.") Yet the advertisement was claimed to be illegal by the FEC because it was aired within 60 days of the general election.
Wisconsin Right to Life vs. FEC