WASHINGTON -- President Obama's campaign has spent nearly $100 million on television commercials in battleground states so far, unleashing a sustained early barrage to create negative impressions of Republican Mitt Romney before he and his allies ramp up for the fall.
More than one-fifth of the ad spending has been in Ohio, a must-win for Mr. Romney more so than for Mr. Obama.
Florida ranks second and Virginia third, according to organizations and other sources that track media spending. Those two states account for roughly half of the Obama's campaign ad spending, according to groups that track spending.
No Republican has ever been elected president without winning Ohio, and Mr. Romney's chances of a victory would be all but extinguished if the President wins either Florida or Virginia.
About three-quarters of the President's advertising has been critical of Mr. Romney as Mr. Obama struggles to turn the election into a choice between him and his rival rather than a referendum on his own handling of the economy.
Mr. Obama's television ad spending dwarfs the Romney campaign's so far by a ratio of 4-1 or more. It is at rough parity with the Republican challenger and several outside GOP-led organizations combined.
The latest attack ad, which began airing Friday, accuses the Republican of favoring a 25 percent tax cut for millionaires, tax breaks for oil companies and corporations that move jobs overseas, and a tax increase for working families.
By contrast, it says, the President wants "the wealthy to pay a little more so the middle class pays less."
Democrats and even some Republicans agree the effort to cast Mr. Romney as an unfit steward for the economy shows sign of making some headway.
Yet GOP strategists hasten to add that the former Massachusetts governor has ample time to counter, particularly with recent signs of a struggling economy and the fall campaign yet to begin.
"Despite all of the negative advertising from the Obama campaign, polling numbers are exactly where they were before they started this onslaught," the Romney campaign said in a memo distributed this week, referring to a rolling average of polls.
Yet Mr. Romney released a scathing ad Thursday to respond to some of Mr. Obama's charges.
In 2008, "candidate Obama lied about Hillary Clinton," the ad said, adding there was no truth to the charges that Mr. Romney was associated with companies that outsourced jobs.
Some surveys suggest shifts in the electoral landscape.
A recent poll by Pew Research Center for the People and the Press found that Mr. Romney has lost ground in the last month on the question of which candidate was better able to improve the economy.
One Republican strategist, speaking on condition of anonymity to avoid offending the campaign, said Mr. Obama's commercials attacking Mr. Romney are quickly defining him and the strategy is effective.
But Carl Forti, one of the strategists involved with Restore Our Future, a political action committee for Mr. Romney, said Mr. Obama's strategy is more defensive than it might appear. "I don't think he's got a choice. He has to try to change the dynamic now, but the polling indicates it's not working. He doesn't appear to be making any headway in the polls."
There is no dispute about the intensity of the general election ad wars, which began in April with Rick Santorum's withdrawal from the race for the Republican nomination.
"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.
Ms. Wilner said viewers in Columbus "are seeing more ads right now than they were seeing in September of 2008." Campaigns traditionally ramp up in September.
The Obama campaign also has advertised in Colorado, Iowa, Nevada, New Hampshire, North Carolina, and Pennsylvania, on both broadcast and local cable.