On Wednesday, the super-PAC supporting President Obama's campaign said they were reserving some $30 million in airtime across six swing states.

But Republicans are likely to dwarf Democratic ad buying efforts. In addition to the Americans for Prosperity buy, the Romney-backing Restore our Future super-PAC is expected to spend aggressively, while outside groups led by former Bush adviser Karl Rove have pledged to spend some $300 million throughout the cycle.