ST. PETERSBURG, Fla. -- Drivers listening to adult contemporary radio along Interstate 4 in central Florida are hearing ads like this: "President Obama raised taxes on Florida's small businesses, and his defense cuts will weaken our military and put thousands more Florida families out of work. Mitt Romney has a better vision for America."
Voters tuning into Top 40 stations in Cleveland or Denver are hearing ads like this: "Mitt Romney's got two degrees from Harvard but wants to cut education funding? Says class sizes don't matter? Come on, man. ... President Obama gets it."
Radio ads, an important component of a presidential candidate's media strategy, are bombarding voters in battleground states much the way such political commercials swamp television. The campaigns and allied independent groups have spent some $20.8 million on radio so far -- much less than the $1 billion they are projected to pour into television ads but a healthy investment in boosting turnout among their most loyal supporters.
"Television is broadcast and radio is narrowcast, so it's much easier for campaigns to track a specific demographic on radio," said Marvin Overby, a political science professor at the University of Missouri who studies radio advertising in campaigns. "Unlike TV, which many people watch on DVR and skip through ads, people listen to radio at work or in their car and are a more captive audience."
Campaigns tend to deliver tougher, more specific messages through radio than they do in television ads, which are widely aired and easy for the opposing campaign to see and respond to.
"Radio is where campaigns throw out red meat -- they can be more raw and more inflammatory," Overby said.
Radio is a campaign's purest form of micro-targeting, best used to reach base voters, not undecided voters, strategists said. Republicans typically place ads on Christian and country music stations and on talk radio, while Democrats make heavy use of urban and Hispanic radio and pop stations to reach younger voters. Both sides are boosting their presence on Pandora, the Internet radio site where listeners build their own channels based on their musical preferences.
"Radio is much more niche than TV -- every radio station is No. 1 in something," Republican radio buyer Alex Patton said. "If you're doing the medium right, it's got to be very targeted to the niche."
A recent radio ad for President Barack Obama in battleground states featured a student named Ronnie Mosley, an urban studies major at historically black Morehouse College in Georgia.
"With Pell Grants, help on student loans and health care reform, President Obama has really given me a shot at the American dream," Mosley says in the ad, airing on radio stations in Colorado, Florida, Iowa, Nevada, North Carolina, Ohio, Pennsylvania, Virginia and Wisconsin.
Both campaigns are advertising heavily on adult contemporary stations to reach women, the campaign's most coveted group of voters.
In Ohio, the campaign's top battleground, the Romney campaign made a pitch to women in suburban areas outside Cleveland with a testimonial from former Ohio Sen. George Voinovich, a popular moderate Republican in the state.
In Virginia, Wisconsin and other closely contested states, the Obama campaign is making ample use of Romney's comments at a secretly recorded fundraiser in Florida earlier this year where he said it wasn't his job as a candidate to worry about the 47 percent of Americans who he said see themselves as victims who feel "entitled" to government assistance.
"He actually said it," the ad says, playing the tape of Romney's remarks. "His job is not to worry about those people?"
In Florida, Crossroads GPS, the conservative advocacy group linked closely to former President George W. Bush's longtime political counselor Karl Rove, is wooing women who voted for Obama four years ago but are disappointed in his record.
"I believed in you, but your promises are as empty as my bank account," a woman's voice says in the ad. "My family can't afford four more years like this. It's time to let President Obama go."
Obama is getting an assist from Planned Parenthood, which recently launched an ad campaign in Virginia and Ohio portraying Romney as a threat to women's reproductive rights.
"Mitt Romney will put critical health care for women and families at risk and will let politicians interfere in your most private, personal medical decisions," the ad says. "President Obama trusts women and knows the health care challenges families face."
Pandora, with 58 million active monthly users, has emerged as a popular advertising destination. Users of the site are required to furnish their ZIP codes when registering, giving campaigns ample data for ad targeting.
Sean Duggan, vice president of advertising for Pandora, said that candidates used to advertise on Pandora primarily to reach younger voters but that the age range has rapidly expanded this year. He said both Republicans and Democrats were advertising equally on the channel and they were rapidly buying up inventory.