"There are more advertisers in fewer markets, spending more money and advertising at a higher frequency than in previous elections," said Elizabeth Wilner, vice president of Kantar Media/CMAG, which monitors advertising.
Wilner said viewers in Columbus, Ohio, "are seeing more ads right now than they were seeing in September of 2008," a period when campaigns traditionally ramp up for the fall. In Iowa, more money has been spent on television ads per electoral vote than in all of 2008, she added.
Obama's campaign has launched four commercials this month, including the attack ad that began during the day.
Two others accuse Romney of having ties to companies that outsource U.S. jobs to low-wage countries overseas. The final one says the former governor supported a law to ban all abortions, including in cases of rape and incest, and wants to end federal funding for Planned Parenthood.
Ads in Ohio, Florida and Virginia account for roughly half of the Obama's campaign ad spending, according to records maintained by groups that track spending and other sources. No Republican has ever been elected president without winning Ohio, and Romney's chances of a victory would be all but extinguished if the president wins either of the two other states.
The Obama campaign also has advertised in Colorado, Iowa, Nevada, New Hampshire, North Carolina and Pennsylvania, on both broadcast and local cable. In some of those states, it has run Spanish-language commercials.
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