The ongoing furor over a TV ad by a pro-Obama super-PAC that implies GOP presidential hopeful Mitt Romney was to blame for the death of a former steelworker’s wife is a rare example of a political commercial that backfires.

The history of political advertising is rich with ultra-controversial ads that have been devastatingly effective, even as they elicited protests from their targets.

Among the most high-profile is the “Daisy Girl” spot that was run only once, by then-President Lyndon Johnson against Sen. Barry Goldwater (R-Ariz.) in 1964. The Johnson ad — shocking at the time — switched from images of a young girl picking a daisy to a nuclear mushroom cloud to target Goldwater as a politician who might lead the U.S. into war.

The Willie Horton ad, deployed by a conservative third-party group against Gov. Michael Dukakis (D-Mass.), drew accusations of racism in the 1988 presidential race. Horton was a convicted felon who raped a young woman while under release on a furlough program. A mug shot of Horton, who was African-American, was used in the ad.

The “Daisy Girl” and Horton ads were both criticized at the time, but are now seen to have helped Johnson and former President George H.W. Bush win election.

By contrast, the Obama team seems to be concerned that the ad by Priorities USA Action, which was prepared but has not been run on television, is hurting them.

During an appearance on MSNBC’s “Daily Rundown” on Monday, former White House press secretary Robert Gibbs suggested that the Romney campaign was trying to keep the story of the ad alive.

“Let me tell you, this has been perpetuated mostly by the Romney campaign,” Gibbs told Chuck Todd. Gibbs declined to say whether the ad made him “uncomfortable,” instead emphasizing that the official Obama campaign was not responsible for it.

The spot itself, in which former steelworker Joe Soptic talks about the death of his wife, Ranae, from cancer, was found to be “misleading on several counts” by, the website run by the nonpartisan Annenberg Public Policy Center. Contrary to the impression given by the ad, Ranae Soptic in fact lost her health coverage after losing her own job and died years after her husband’s steel plant was closed down. Joe Soptic worked at GST Steel, which was closed down after being bought out by Romney's Bain Capital.

“It backfired because it gave Republicans the opening to say that Obama and the Democrats are lying overtly in their advertising,” said Tobe Berkovitz, a Boston University professor and an expert on political commercials.

He added: “The Obama ad campaign has so far been relatively effective. This, of course, is not an official Obama ad. But ‘civilians’ don’t discern much difference between a candidate’s ad and a Super PAC ad.”

Professor John Geer of Vanderbilt University, the author of a book in defense of negative advertising, noted that it was relatively rare for campaign ads at the presidential level to backfire. Counterproductive ads, he said, were more common in congressional races.

In contests for the White House, Geer said, “you have two really good candidates with two really smart campaign teams. In congressional races, you often have two really bad candidates with really bad teams, and so they say things they should not say.”

Still there are occasional misfires even at the highest level. Geer cited the example of an ad run by Sen. John McCainJohn Sidney McCainTrump's NASA nominee advances after floor drama Senate repeals auto-loan guidance in precedent-shattering vote Overnight Defense: Lawmakers worry over Syria strategy | Trump's base critical of strikes | Flake undecided on Pompeo | Coast Guard plans to keep allowing transgender members | GOP chair wants to cut B from Pentagon agencies MORE (R-Ariz.) in 2008 accusing his opponent, now the president, of having supported sex education for kindergarteners.

The Annenberg center called the ad’s central claim “simply false.”

“That ad probably hurt McCain,” Geer said. “It was just not credible.”

Still, as both experts noted, storms over negative ads occur fairly regularly — and tend to blow over quickly.

“Most of the time, it’s a tempest in a teapot,” Berkovitz said.

This story was updated at 1:10 p.m.