WASHINGTON - Already, both sides in the presidential race have loosed the electronic dogs of war.

On TV sets in Pennsylvania and other battleground states, it already looks like the first week of October, as the candidates and free-spending super-PACs working on their behalf launch attacks and counterattacks unprecedented in size, cost, and negativity for so early in the campaign.

The strategic aim, of course, is to define your opponent before he can define himself, to begin hardening unflattering perceptions that can be reinforced by the onslaught to come.

"There's never been this much of it this early, most of it attack-based," said Kathleen Hall Jamieson, director of the Annenberg Public Policy Center at the University of Pennsylvania. "It's driven by the third-party groups, and we know historically that their ads tend to be more negative and deceptive."

President Obama's campaign and Priorities USA, a super-PAC, bought $29 million worth of airtime to run ads through the end of May in Pennsylvania, Ohio, Nevada, New Hampshire, Iowa, North Carolina, Florida, and Colorado.

They are seeking to turn a perceived Romney strength - his business experience - into a weakness by ripping his record as head of the private equity firm Bain Capital, highlighting workers whose lives were upended when Bain bought their companies, saddled them with debt, and then let them go bankrupt while Romney and his partners profited.

It's also a way to keep the focus on Romney and not on Obama's first term, with its economic woes.

Crossroads GPS, the Republican super-PAC cofounded by Karl Rove, launched $25 million worth of attack ads last week in those same states, plus Michigan. The first wave was a spot accusing Obama of broken promises, with a narrator tolling the continued wave of home foreclosures, the sluggish recovery, and the skyrocketing federal debt as a hammer shattered an iPad's glass screen.

On Wednesday, Crossroads is changing up its attack with a softer, 60-second spot called "Basketball," featuring a woman in her kitchen - a recurring image in this year's campaign ads - watching her kids playing hoops in the driveway as she talks of her family's financial woes.

Her face morphs into that of an older woman; her children, now grown, have moved back home because they can't find jobs; she worries whether she can retire.

"I supported President Obama because he spoke so beautifully," the woman says. "He promised change. But things changed for the worse."

Jamieson predicts the negativity will continue. At a site called FlackCheck.org, the Annenberg center is helping viewers petition TV stations to resist the worst super-PAC attacks. Though stations must accept ads from presidential campaigns, they have more discretion to seek modifications or even reject ads outright if they come from independent groups.

The Wesleyan Media Project at Wesleyan University in Connecticut analyzed campaign ads aired between Jan. 1, 2011, and the end of April, and found 70 percent were attacks on opponents, compared with 10 percent at the same point in the 2008 campaign. In part, that is due to the Republican primary fight that ended in April.

The study also tallied independent groups' ads aimed at general-election themes: 33,420 anti-Obama, pro-Republican spots aired, compared with 25,516 anti-GOP, pro-Obama spots.

Trying to define your opponent early is not new. Then-President George W. Bush spent $40 million from March through mid-May 2004 on attack ads portraying Democrat John Kerry as weak on national security and tax-happy, Bloomberg News found.

One important difference: The 2004 spending was by Bush's own campaign, while this year, the action is centered on the super-PACs and nonprofits freed by the 2010 Supreme Court Citizens United ruling to spend unlimited corporate and union funds directly on ads.

That, in turn, gives candidates some deniability - super-PACs, by law, cannot coordinate efforts with candidates. And good luck learning whose cash bought the ads; Crossroads GPS's website assures would-be donors that the super-PAC's policy "is to not provide the names of its donors to the general public."

"The majority of general-election airings and spending has come from groups that do not need to disclose their donors," Michael M. Franz, codirector of the Wesleyan project, said in a study published May 2. "That's a lot of money and airtime backed by undisclosed sources."

Susan Petro, who handles sales of political ads for WJLA-TV in Washington, the ABC affiliate, said the buying has been intense since Virginia became a swing state.

"Crossroads GPS was in this market in November [2011]," Petro said Tuesday during an Annenberg-sponsored "Fact Checking the 2012 Election" symposium at the National Press Club in Washington. "Being that Virginia is highly contested, we have ad time on the books already for October. We've never seen it that early."

As for Pennsylvania, the blitz signals that the Romney campaign and its GOP allies regard the state as being in play at this point - though Democrats have carried it in every presidential election since 1988.

Sometimes, there is push-back - such as what Obama is facing for the Bain attacks from elements within his party, including Newark Mayor Cory Booker, a top surrogate, who on Sunday called the attacks "nauseating."

"I'm not going to sit here and indict private equity," Booker said on NBC's Meet the Press. "If you look at the totality of Bain Capital's record, they've done a lot to support businesses, to grow businesses, and this, to me, I'm very uncomfortable with."

He quickly softened his critique by Sunday night, but other Democrats, including former Pennsylvania Gov. Ed Rendell, have also second-guessed the Bain attacks.

Analysts warn that attack ads tend to drive down turnout as voters sour on the candidates and the process.

"The question is," Jamieson said, "will we have an election when there's nothing to vote for?"

at 215-854-2718 or tfitzgerald@phillynews.com or @tomfitzgerald on Twitter. Read his blog, "The Big Tent," at www.philly.com/bigtent.