With 100 days remaining before Election Day, there is an air of apprehension around the Obama campaign headquarters here. Yet there are few regrets about the tone of the race, only a conviction that the circumstances — a frail economy, intense Republican opposition and a well-financed negative campaign from Mr. Romney and his allies — left Mr. Obama no option but to fight back even if it sullies his image as a candidate of hope and change.
“Is it a different kind of race than 2008? Of course,” said David Axelrod, a senior campaign strategist. “If we were passive in the face of this onslaught we are facing, our folks would be unhappy. There are few on our side who are counseling us to sit idly by.”
Mr. Romney and his allies are giving as good as they get, lacerating Mr. Obama as hapless in promoting job creation, feckless with allies like Israel and determined to expand government until the United States resembles Sweden.
As the campaigns prepare for the next phase of the race, the two sides are taking stock of what they have achieved in their first sustained engagement, a relentlessly negative effort over the last two months to define the other. The exchanges have been so fierce that hardly a positive ad has been broadcast in July.
But both the opportunities and the risks in the definition wars are greater for Mr. Obama. Mr. Romney is less well known to the public, giving Democrats a chance to shape perceptions of him just as more voters are starting to tune in to the race.
The president’s prospects for re-election now rest in part on one of the biggest gambles of his career: that the benefits of trying to eviscerate Mr. Romney outweigh the costs to his own image and reputation.
With a political climate ripe for unseating an incumbent, the president’s campaign team signaled long ago that it had no intention of trying to replicate the 2008 race, and made it clear last year that if Mr. Romney won the Republican nomination, they would rush to aggressively define him before turning to a forward-looking message in the fall.
Mr. Obama, whose competitive and confident streaks seem to have been rekindled by the challenge from Mr. Romney, has shown no inclination to hold back in trying to portray his rival as a secretive Bush-era throwback whose wealth puts him out of touch with the middle class.
The president not only approves of his television ads, as federal election law requires him to say in each commercial, he also screens many of them in advance, either on his iPad or during a regular Sunday evening meeting with political advisers at the White House.
Fearful of the tone becoming too shrill, he took the rare step of speaking directly to the camera in a new ad that elevates the conversation, a hint of his approach when the campaign moves beyond summer.
“Sometimes politics can seem very small,” Mr. Obama said, sounding almost apologetic. “But the choice you face, it couldn’t be bigger.”
His aides wondered in particular whether a recent spot showing Mr. Romney singing “America the Beautiful,” while headlines about outsourcing and overseas bank accounts flashed, was too negative. The president and some of his strategists were unsure, aides said, but a focus group of voters found it to be fair. They still tested the ad again before showing it.
The ratio of negative ads, which are defined as those in which a campaign mentions its rival by name, tells the story. Since April, after Mr. Romney became the presumptive nominee, Mr. Obama broadcast negative commercials 118,775 times compared with 56,128 times for positive commercials.
In the same time period, Mr. Romney ran negative spots 51,973 times and positive spots 11,921, according to an analysis from Kantar Media, which tracks political advertising. This does not include the Republican “super PAC” ads that are almost entirely attacks on the president.
“President Obama was keeping a more balanced mix, but by the end of June he turned off the positive spigot,” said Elizabeth Wilner, who studies advertising for the group.
Polls suggest that voters might be starting to view Mr. Obama less favorably even as the race remains tight. And while it is hard to know whether the shift is related to the tone of his campaign, his advisers are acutely mindful that one of Mr. Obama’s key attributes, that voters generally like him, must be preserved to win over the undecided voters who will determine the race.
But if Mr. Obama prevails, it will almost certainly be because his team executed a plan to try to win the race in the summer to make Mr. Romney unacceptable to voters by the fall. It is a page from the 2004 playbook of President George W. Bush, whose campaign spent the same period relentlessly defining Senator John Kerry as unreliable.
Matthew Dowd, a former Republican strategist who was a top adviser on the Bush re-election campaign, refers to it as “poisoning the water table.” The parallels between 2004 and 2012 are striking, he said, with the Obama campaign putting its stamp on Mr. Romney before he introduces himself to voters.
“President Obama and his campaign have made the determination that the only way they can win this race is to create a negative impression of Mitt Romney,” said Mr. Dowd, now an independent analyst. “When people go to vote, even if they don’t like the direction of the country, they may not trust Mitt Romney.”
Republicans are trying to seize on the tone of the campaign and turn it against the president, with a recent ad titled, “Whatever happened to hope and change?”
Still, the respective Republican groups have spent far less time either introducing Mr. Romney or defending him. Some party leaders now wonder whether that was a mistake, given that the questions about his tax returns or his time at Bain Capital have become ubiquitous.
But despite tens of millions of dollars spent on ads this summer, the race remains essentially deadlocked. The Romney campaign is within striking distance in nearly every battleground state, aides to both campaigns say, with the president still holding more paths to reaching the 270 electoral votes needed.
While Mr. Obama rose through the ranks with a clarion call for a new kind of politics, there is little noticeable criticism about the tenor of the race from longtime supporters.
“There is no question the atmosphere is different than the last campaign. It has to be,” said Judd Miner, a Chicago lawyer who has known the president for two decades and still refers to him by his first name. “We learned the hard way with Kerry. It matters that Barack wins.”