In two races for the US Senate, candidates have filed defamation lawsuits against their opponents charging that attack ads go over the line from political argument to actionable falsehoods. However these suits ultimately play out, they demonstrate the premise that we've written about before, that broadcast stations are prohibited by FCC rules and the Communications Act from censoring the content of a candidate's ad, and because they cannot censor the content of a candidate's ad (or refuse to run a candidate's ad because of the content of that ad), stations are immune from liability that might otherwise arise from that content. But the candidates being attacked can sue their opponents for the contents of those ads, and that is just what has happened in the North Carolina and Minnesota Senate races.
In North Carolina, according to press reports, Democratic candidate Kay Hagan has filed suit against the campaign of Elizabeth Dole for a commercial that accused Hagan of being associated with a group called Godless Americans - an ad ending with a woman's voice that some interpreted as being that of Hagan (when it was in fact not) saying "there is no God." In Minnesota, Senator Norm Coleman has reportedly filed a lawsuit against Al Franken's campaign claiming that Franken campaign ads improperly claimed that Coleman was rated one of the four most corrupt Senators and that he was getting an improperly financed apartment in Washington DC.
Defamation is very difficult to prove, especially when the statements are made against public figures, such as political candidates. A plaintiff must prove that the statement that was made is false, and that the person making it either knew that it was false, or made it with reckless disregard of the truth of the statement (what the Supreme Court has called the "malice" standard). As it is so difficult to prove malice in a political context, the filing of lawsuits such as these are rare, and they are seldom if ever prosecuted through to any sort of judgment.
If these lawsuits are so hard to prove, why bring them? In some cases, where the conduct really is outrageous, there may be grounds for a recovery. In other cases, the suit can be brought to scare media outlets into not running the ad (even though a broadcast station should not refuse to air an ad based on its content if the ad is bought by the candidate's authorized committee) or to delay the airing of the commercial while the broadcast station considers whether or not it should be run. In these waning days of an election, having an ad run a few fewer times may be a strategic victory.