PUEBLO, Colo. — Mitt Romney and President Barack Obama both deplored the pervasive presence of televised attack ads in the race for the White House on Thursday, though neither acknowledged being helped as well as harmed. Each blamed his foe.

Romney went first, saying of the president’s campaign, “They just blast ahead” with ads that have been judged false by independent fact checkers.

“I don’t know whatever happened to a campaign of ‘hope and change,”’ he said, a mocking reference to the spirit of optimism that Obama evoked during his successful run for the White House in 2008.

Obama ignored the slap. He told an audience in Colorado that “over the next three months, you will see more negative ads,” and he suggested the blame lies with outside groups backing his rival.

“I mean, these super PACs, these guys are writing $10 million checks and giving them to Mr. Romney’s supporters,” he said.

Obama spoke as his own campaign unleashed yet another in the attack ad category, this one questioning whether there was ever a year in which Romney paid no federal taxes. ‘We don’t know,” the announcer says, then quickly adds that Romney once “personally approved over $70 million in fictional losses to the IRS as part of ... one of the largest tax avoidance schemes in history.”

Romney broached the subject two days after the release of a searing ad in which a former steelworker appears to suggest that he and Bain Capital, the private equity firm he owned, might bear some responsibility for the man’s wife’s death from cancer. The ad is the work of Priorities USA Action, a group that supports Obama, and it has been judged inaccurate by independent fact checkers and attacked vociferously by aides to the GOP presidential challenger.

The back and forth took place as Romney looked ahead to a bus tour through four states in as many days, ending next Tuesday in Ohio. The itinerary renewed speculation that the trip might culminate in the announcement that the state’s Sen. Rob Portman would be the named vice presidential running mate on the Republican ticket.

Obama barnstormed through battleground Colorado more like a candidate for statewide office than for the White House, with stops in several parts of the state over two days.

After saying in Denver that Romney advocated policies on women’s issues straight from the 1950s, he switched topics to alternative energy. Campaigning in Pueblo, the president noted that his rival wants to end a tax credit that benefits the producers of wind energy, an industry that Obama said supports about 5,000 jobs in Colorado and as many as 37,000 nationwide.

“It’s time to stop spending billions in taxpayer subsidies on an oil industry that’s already making a lot of profit, and let’s keep investing in new energy sources that have never been more promising,” he said.

Three of Colorado’s four Republican House members support the credit, as do senior Republican office holders in Iowa, another presidential battleground state where Romney’s opposition puts him at odds with the GOP establishment.

At issue is a tax credit that was originally signed into law 20 years ago by President George H.W. Bush, a Republican, and has generally enjoyed bipartisan support in the years since.

Legislation headed for the Senate floor would renew the tax break for existing facilities for one year, and also allow facilities that begin construction before the end of 2013 to qualify for a 10-year credit. The estimated cost is $12.1 billion over a decade, and the tax break has drawn criticism from some conservatives in Congress as a waste.

Romney sides with the critics, and in March he wrote, “In place of real energy, Obama has focused on an imaginary world where government-subsidized windmills and solar panels could power the economy. This vision has failed.”  

In the clash over television advertising, Romney appeared to lump together commercials aired by Obama’s campaign with those aired by Priorities Action USA, the group that supports him.

In his remarks to conservative radio show host Bill Bennett, Romney aides said, he was speaking about the Priorities Action USA commercial when he attacked the president’s campaign.

By law, candidates’ campaigns are not allowed to coordinate with independent groups that are aligned with them.

But most political experts agree that the finer points of campaign law are lost on most voters, who tell pollsters they dislike attack ads yet are known to shift their views of candidates because of them.

There is no dispute about their prevalence.

Obama, Romney and super PACs supporting both men have been running such ads for months at a cost of millions of dollars.

Restore Our Future, an independent group that backs Romney, aired ads during the race for the Republican nomination that first crippled Newt Gingrich and then sent Rick Santorum to the sidelines. The group spent more money on ads during the primary season than Romney’s own campaign.

The same group as well as American Crossroads and Crossroads GPS have aired ads critical of Obama in more recent weeks, outspending candidate Romney, who can’t fully dip into his campaign treasury until after the GOP convention in Tampa, Fla., this month.

Priorities Action USA went after Romney in the ad that sparked this week’s controversy.

In such cases, accuracy is not always observed.

This week, Romney accused Obama in a commercial of planning to “gut welfare reform” by dropping work requirements. Gingrich, now a Romney supporter, said there is “no proof today” of the claim.

Last February, Gingrich, then a presidential contender, asked Georgia television stations to remove an attack ad by Restore Our Future. It accused him of once having co-sponsored legislation that sent $60 million a year to U.N. programs supporting China’s “brutal one-child policy.” PolitiFact, an independent website, rated the charge as false, but the ad was not taken down.

Obama’s campaign last month aired an ad saying that Romney “backed a bill that outlaws all abortion, even in cases of rape and incest.” FactCheck.org found that Romney’s consistent position at least since 2005, is to oppose abortion except in cases of rape, incest or when the life of the mother is in danger.

In this week’s controversy, Priorities USA Action says it has no plans to remove the commercial that prompted Romney’s comments to Bennett.

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Associated Press writers Kasie Hunt in New York and Steve Peoples and Philip Elliott in Washington contributed to this story. Julie Pace reported from Colorado.