Story highlights Campaigns and supporters of President Obama, Mitt Romney trade caustic barbs

The White House calls a Republican ad on welfare changes "blatantly dishonest"

The Romney campaign calls an Obama super-PAC ad "discredited and dishonest"

With the election less than three months away, both sides are buying more ad time

Hypocritical. Contemptible. Dishonest. "Obamaloney." The rhetoric, charges and counter-charges flew fast and thick Tuesday as the presidential election campaign continued on its sharply negative trajectory.

New advertisements by each side prompted caustic responses from the other as name-calling and finger-pointing dominated the debate less than three months before the November vote that pits President Barack Obama against certain Republican nominee Mitt Romney.

A day after Obama coined the phrase "Romneyhood" to describe policies by Romney that Obama said tax the poor to help the rich -- or Robin Hood in reverse -- Romney fired back by creating his own word -- Obamaloney -- to accuse the president of making things up.

"He is serving up a dish that is in contradiction to the truth," Romney told Fox News.

Meanwhile, a Romney ad that began airing Tuesday accused Obama of seeking to undermine work requirements in a bipartisan welfare reform law signed by President Bill Clinton in 1996.

JUST WATCHED Obama criticizes 'Romney Hood' tax plan Replay More Videos ... MUST WATCH Obama criticizes 'Romney Hood' tax plan 01:01

JUST WATCHED Reid vs. Romney: The battle continues Replay More Videos ... MUST WATCH Reid vs. Romney: The battle continues 04:49

JUST WATCHED Romney hits Obama for welfare changes Replay More Videos ... MUST WATCH Romney hits Obama for welfare changes 03:05

White House spokesman Jay Carney rejected the claim, telling reporters that the ad was "categorically false" and "blatantly dishonest."

"This administration's policy will strengthen the (welfare) program by giving states the opportunity to employ more effective ways," Carney said.

Following a weekend imbroglio over Senate Majority Leader Harry Reid's claim that a former Romney associate told him Romney paid no taxes in past years, the campaign has veered into a political mud pile that emphasizes dirtying the opponent first.

The tactics are part of the big-picture efforts by both sides to frame the election in terms favorable to their man. For Romney, that means portraying Obama as a failed president unworthy of a second term. For Obama, that means depicting the former Massachusetts governor as a champion of the wealthy class and special interests.

Reid's unsubstantiated claim, based on an unidentified source, was intended to keep alive the push by Democrats to force Romney to release more of his past tax returns than the two years disclosed so far -- his 2010 filing and an estimate for 2011. Romney says he will make public the final version of last year's return.

Democrats know that whatever any additional returns show, they can highlight the details of tax breaks and other accounting maneuvers by the multimillionaire Romney to bolster the perception they seek to exploit that he represents society's fat cats.

Republicans responded by attacking Reid's credibility, and by extension, the president's also.

Romney called on Reid to disclose his source or shut up, insisting he paid lots of taxes in past years, while top party spokesmen and surrogates called Reid a liar and said he was carrying out the attack at the request of the White House.

Obama advisers, benefiting from the continued focus on the matter, denied they were behind Reid's push.

"There is a way to resolve this dispute ... which is for the governor to follow a tradition that was established by his own father many years ago of presidential candidates releasing multiple years of his tax return," White House spokesman Carney chimed in Tuesday.

Carney referred to the decision by George Romney, the former Michigan governor who released 12 years of his tax returns when running for president in 1968. Mitt Romney says he has complied with the law and won't release any further returns that would only get distorted by Democratic attackers.

Earlier Tuesday, a Romney ad on welfare changes by the Obama administration claimed they would "gut welfare reform by dropping work requirements."

"Under Obama's plan, you wouldn't have to work and wouldn't have to train for a job. They just send you your welfare check," the announcer says. "And welfare-to-work goes back to being plain old welfare."

The changes, which would allow states greater flexibility in administering their welfare-to-work programs, were in a directive issued last month by the Department of Health and Human Services.

At the time, some Republicans claimed the new rules amounted to a "gutting" of work requirements for welfare recipients, which were a central element of the bipartisan welfare reform law signed by President Bill Clinton in 1996.

The fact-checking website PolitiFact.com said Tuesday that the Romney ad distorted the intent of the welfare changes and gave it its harshest ruling of "Pants on Fire." In addition, Clinton issued a statement saying the Romney ad was wrong.

Carney responded with unusually strong language at his daily briefing.

"This advertisement is categorically false and it is blatantly dishonest," Carney said. "This administration's policy will strengthen the program by giving states the opportunity to employ more effective ways."

He also called Republican criticism of the changes "hypocrisy," pointing to past support from Republican governors -- including Romney -- for waivers to the federal requirements. In addition, Carney said, Republican governors in Nevada and Utah already are seeking waivers under the administration's program.

Obama's re-election campaign, meanwhile, accused Romney of "not telling the truth."

"The truth is that the president is giving states additional flexibility only if they move more people from welfare to work - not fewer," Obama campaign spokeswoman Lis Smith said in a statement. " ... By falsely attacking a policy that both he and his Republican allies have supported for years, Romney is once again flip-flopping on a position he took in Massachusetts, and demonstrating that he lacks the core strength and principles the nation needs in a president."

Romney campaign Policy Director Lanhee Chen insisted that Romney has remained consistent in supporting work requirements for welfare recipients. Chen's statement said that as Massachusetts governor, "Romney vetoed efforts to weaken work requirements and he pressed repeatedly to instead strengthen them and bring them in line with federal standards."

Also Tuesday, a super-PAC supportive of Obama released a new ad tying Romney to the death of a former GST Steel worker's wife after her husband lost his job when the plant closed down.

Romney's former private equity firm, Bain Capital, acquired GST Steel in 1993, but the company went bankrupt in 2001, two years after Romney ceased day-to-day oversight of Bain.

The ad by Priorities USA Action features Joe Soptic, a former worker at the Kansas City-based steel plant, as he tells the story of how he lost health insurance benefits when the plant shuttered. He then says his wife passed away from cancer after that. Soptic's wife died in 2006.

"I do not think Mitt Romney realizes what he's done to anyone, and furthermore I do not think Mitt Romney is concerned," Soptic says.

Romney's campaign issued a harsh reaction.

"President Obama's allies continue to use discredited and dishonest attacks in a contemptible effort to conceal the administration's deplorable economic record," Romney spokeswoman Amanda Henneberg said in a statement.

Expect more of the same. Last week, CNN reported that Priorities USA Action has reserved $30 million this fall for broadcast and cable time. And on Tuesday, a major fiscal conservative group that has spent tens of millions of dollars on ads critical of Obama revealed it will spend at least $7 million for new spots starting Wednesday in 11 battleground states: Colorado, Florida, Iowa, Minnesota, Nevada, New Mexico, North Carolina, Ohio, Pennsylvania, Virginia, and Wisconsin.

Americans for Prosperity, which is partially funded by the influential Charles and David Koch, said it will rotate different ads and messages over the next three weeks in the campaign that could cost as much as $27 million.

The billionaire Koch brothers are high-profile figures in the Republican Party who support conservative and libertarian causes. Backers of Americans for Prosperity, the pair of industrialists are expected to spend tens -- if not hundreds -- of millions on Republican causes this year.