From a New York Times report:
Negative advertisements have hit the airwaves early as Democrat candidates fight to preserve the party's congressional majority.
Democratic candidates across the country are opening a fierce offensive of negative advertisements against Republicans, using lawsuits, tax filings, reports from the Better Business Bureau and even divorce proceedings to try to discredit their opponents and save their congressional majority.
Opposition research and attack advertising are deployed in almost every election, but these biting ads are coming far earlier than ever before, according to party strategists. The campaign has intensified in the past two weeks as early voting begins in several states and as vulnerable incumbents try to fight off an onslaught of influences by outside groups.