The largest effect of the Citizens United ruling is probably not the Presidential race, which is sufficiently well-funded for messages to get out on both sides. And, for the moment, that race looks hard to flip.
However, Congressional and state races are another story. Imagine if you had $50 million to distribute to 5 critical Senate races and 20 critical House races. Each race could get $2 million to set up a mini-think tank, opposition research, and a viral campaign. That would buy a lot of local messaging and mudslinging. And a lot of robocalls. By modern standards, $50M is not a lot of money. By the same logic I’ve applied to leveraging your campaign donations, a Super PAC would be well advised to do the same thing. Indeed, Karl Rove’s groups are doing exactly this.
The same is doubly true for state politics. For some of these races, even $20,000 is a lot. New fluxes of money into local races are a major emerging story in Campaign 2012.