The supreme court ruled that corporations could not be restricted in the money they spend on elections. This will also unleash unions to spend more than ever.

The same ruling also reversed the McCain Feingold law that kept corporations and unions from running ads within a certain date before elections.

The NY Times reports, "The court on Thursday overturned a 20-year-old ruling that said
corporations can be prohibited from using money from their general
treasuries to pay for campaign ads. The decision almost certainly will
also allow labor unions to participate more freely in campaigns and
threatens similar limits imposed by 24 states."