"In Colorado, Florida, Georgia, Missouri, Ohio, Pennsylvania, and Virginia, Obama placed 155% more ad units (62,022 vs. 24,273) than McCain between October 6 and October 26, 2008.

As of October 22, Obama had placed 150% more ad units (53,049 vs. 21,106) than McCain in those key battleground states.

Obama's advertising continues to be heaviest in Florida, where he ran 18,909 ads between October 6 and October 26, outpacing McCain's 5,702 ads by 232%.

In recent days, McCain has closed the gap slightly, boosting his ad units by 22% in Florida - up from 4,662 units as of October 22. In comparison, Obama increased his ad units in the state by just 19% between October 22 and 26.

In Ohio, where McCain's advertising has been most prolific during the last three weeks (5,800 units), Obama ran 15,227 ad units between October 6 and October 26, besting the GOP contender by 162%." -- Nielsen

This is a big part of the reason why McCain is having such a tough time right now. With the mainstream media essentially acting as a wing of the Obama campaign, McCain has to rely heavily on ads to get his side of the story out. When Obama can afford to run 2 or 3 times as many advertisements in key swing states, even if McCain has a better message, it's difficult for him to make up ground under those circumstances.