The presidential campaign is erupting into a full-scale advertising war, with both candidates and their allies pouring huge sums into early and aggressive efforts to define the fight on their terms.

At least $50 million worth of ads will appear in swing states in the next several weeks as President Barack Obama and Mitt Romney move swiftly to win over voters now, casting aside concerns that their money will be wasted on people who are not paying much attention 5 1/2 months before Election Day.

The latest volley came Wednesday, when Crossroads GPS, a political group formed by Karl Rove and other top Republican strategists, unveiled a $25 million advertising campaign. The group opened with a hard-hitting commercial that casts Obama as a failed leader, unable to deliver on his pledges to fix the country’s problems.

“President Obama’s agenda promised so much,” it says over the sound of breaking glass. “He hasn’t even come close. We need solutions, not just promises.”

The Crossroads ad campaign matches the $25 million advertising offensive that the Obama campaign began last week. Other outside political groups and “super PACs” have committed at least an additional $15 million in recent weeks, mostly to Romney’s benefit, according to Kantar Media.

There is almost certainly more to come before the highly viewed spring television schedule winds down for the summer. Many central players, including the Democratic and Republican Party committees and Romney’s campaign, have been largely absent from the TV in recent weeks and are sitting on large piles of cash. Romney, who had more than $10 million in the bank at the end of March and has been aggressively raising money in the past few weeks, has not advertised since Rick Santorum dropped his bid for the Republican nomination a month ago.

Such a high volume of ads coming before the summer — many of them negative and concentrated in a handful of battleground states — further reinforces the belief among political strategists that this election will see an unusually heavy and vicious air war as outside political groups assume a larger role than ever.

In dueling sets of ads, each side offers its perspective on the progress, or lack thereof, that the country has made under Obama. The new Crossroads ad pushes the narrative that despite his lofty vision for a better America, Obama — and indeed the nation — has made little progress in 3 1/2 years.

In its ads, the Obama campaign tries to remind voters of the deep economic crisis the president inherited and argues that he has set the country on the right path.

“It’s still too hard for too many,” the opening ad of his $25 million campaign says. “We’re not there yet. It’s still too hard for too many. But we’re coming back.”

In previous years, ad spending has been heavy but not as focused on such a small number of states. In 2004, for example, George W. Bush’s campaign was spending $5 million every week on television ads after Sen. John Kerry emerged as the Democratic nominee. But the campaign initially spread its advertising over 17 states.

“I think the key word is concentrated,” said Kenneth M. Goldstein, president of Kantar Media’s Campaign Media Analysis Group. “This tells us that it’s not 13 or 14 states that matter. It’s seven or eight.”

With the Crossroads ads, set to start running Thursday, the president and his opponents will be on television head to head in nine states: Colorado, Florida, Iowa, Nevada, New Hampshire, North Carolina, Ohio, Pennsylvania and Virginia.

The rush to advertise now reflects a belief among political strategists on both sides that they have a small window of time to frame the election.

Only a few weeks remain before the busy television-watching season slows down and summer reruns begin. The Olympics start at the end of July, a time when most Americans will hardly be thinking about politics. Many strategists believe they will not have an opportunity to connect with voters again until the political conventions begin in late August.

“The first ads that are run are in many ways the most important because the mind is the most open and uncluttered at that point,” said Carter Eskew, a veteran Democratic strategist.

By late summer and early fall, he said, political advertising has reached the saturation point.

“Most people are sick of it because you have ads for president, then Senate, then dog catcher and assistant dog catcher,” he said. “It’s back to back to back.”

The new Crossroads campaign fills a void in those crucial states. Romney’s super PAC has been running ads sporadically, including a sarcasm-laden Mother’s Day spot that took notable Democrats to task for their dismissive comments about Ann Romney, a stay-at-home mother.

“Happy Mother’s Day from Barack Obama’s team,” said the narrator, a soft-spoken woman.

Romney, however, has been quiet. Stuart Stevens, a senior Romney strategist, would not elaborate Wednesday about the campaign’s plans. But Romney videographers have been interviewing people across the country about their economic woes.

The role of super PACs in providing that auxiliary support has been essential, experts said.

“It’s to your advantage to offload your work to the super PACs,” said Erika Franklin Fowler, director of the Wesleyan Media Project, which tracks political ads. “In a world in which campaigns can’t technically coordinate with super PACs, one way of doing things is waiting to see what the other is doing and then filling in the gaps.”