Those advertisements aren't seen in vast areas of the country, including huge population centers such as California and New York whose leanings in the presidential race don't appear in doubt. Instead, they air principally in a handful of swing states that the Obama and Romney campaigns are battling over, including Ohio, Florida, Iowa, Nevada, Colorado, New Hampshire, North Carolina and Virginia.
Just this week, the competing Republican and Democratic political armies have spent some $21 million in only 10 states, according to figures compiled by the media firm SMG Delta. Those armies have different units; aside from the Obama and Romney campaigns, there are so-called "super-PACs" backing the president (Priorities USA) and his Republican rival (Restore Our Future, Crossroads GPS).
In the last week, for instance, the Obama campaign has spent $1.5 million on ads in Florida, buttressed by another $273,000 by Priorities USA. The Romney campaign spent just $450,000 but enjoyed a slight advantage anyway, since Crossroads GPS spent $1.7 million.
In Ohio, Obama outpaced Romney in direct spending, $1.4 million to $311,000. But $930,000 worth of ads by Crossroads GPS and $865,000 by the Republican National Committee wiped out that edge.
Their messages by units on each side are distinct but overlapping.
In this ad featuring footage from CNBC, Crossroads slams Obama's approach to the economy. In this one, Restore Our Future hits Obama for having said America's private sector is "doing fine." In this one, the Romney campaign targets Obama for going negative.