There's probably no more compelling evidence of the fall of America's unions than the Twinkie.

After Hostess filed for bankruptcy last November when its bakers' union ordered a strike, a good chunk of the nation decided that a greedy union was at fault for endangering an American institution. Never mind the fact that the synthetic snack was more loved than purchased in a world gravitating toward more-healthful alternatives.

It's just the latest in a string of problems organized labor has been blamed for over the years, among them unemployment, the shipping of jobs to China and the decline of the auto industry. In January, the Bureau of Labor Statistics found the percentage of American workers who belong to a union is at just over 11%, a 97-year low. And public perception of unions has been trending downward for decades, according to an oft-cited Gallup poll that in 2011 reflected dissatisfaction with unions near an all-time high.

The decision of major unions to eschew marketing strategies in the face of major perception challenges is noticeable, especially when you apply a historical lens to high-profile efforts that rival the best of big-brand marketing for memorability.

In the 1970s, "Look for the Union Label" became a pop-culture mainstay. The late 1980s "Union Yes" campaign drew celebrity turns from the likes of Jack Lemmon and Tyne Daly.  

Gary Chaison, professor of industrial relations at Clark University, offered three reasons why union ad budgets could be declining. Unions, he said, are focused more on their workers than on the general public and they direct their ads to locations where union-organizing drives are under way.

Second, big chunks of ad budgets have gone to political campaigns, get-out-the-vote efforts and tying specific issues like health-care reform, immigration and globalization's impact to candidates they support.

And, he said, "union membership has fallen and members' dues are the primary source of union revenues. So unions have less to spend because, with fewer members, they are taking in less."

There have been recent attempts to rekindle the marketing magic. Early last year the AFL-CIO launched an integrated campaign under the tagline "Work Connects Us All."

In contrast to union ads of the past, the creative focuses not on the achievements or benefits of union membership but offers a paean to work with less-than-rousing observations such as "Work is what we do to better ourselves."

The ad copy led a Chamber of Commerce executive to remark to The Wall Street Journal, "No one questions the value of work, but that doesn't really relate to whether one wants to join a union."

George Lois, the iconic ad man responsible for the AFL-CIO's old "Union Yes" campaign, had tougher words for the newer effort. "It's just as unfocused as most advertising in America today," he said. "As unions lose their power, that doesn't mean their advertising has to be weak and ambiguous," he said. "They almost seem to be embarrassed. They don't even say the word 'union.'"

The AFL-CIO said the campaign improved favorability numbers by 10 points in Pittsburgh, eight in Portland, Ore., and four in Austin. Although the TV campaign was never expanded beyond those test markets, the union and its agency, SS&K, is proud of an ongoing digital effort and stands by the choices of messaging and tone.

"As unions are less present in people's lives, we need to create an emotional connection," said Denise Mitchell, spokeswoman for the AFL-CIO. "We tested a lot of different approaches. A pure-benefits [approach] isn't the best way to reach people. It's a good supporting point, but we need to connect around common values."

Ms. Mitchell said that tighter budgets require more targeting and more digital communications. The "Work Connects Us All" campaign cost a reported $1.5 million; "Union Yes," an effort that launched in 1988, cost AFL-CIO $13 million. This serious investment, financed by a 4-cent increase in monthly union dues, would be $25 million today, adjusted for inflation.

The union estimated that 91% of American homes with TVs would catch the "Union Yes" ads at least four times.

But there was a rub, Ms. Mitchell said. "Our internal evaluation is that it was hugely popular among members -- they loved seeing the union legitimized on TV -- but it didn't produce any breakthroughs with non-union members. It was too transactional, too much of a sales pitch."

Of course, nothing, including that campaign, has stemmed labor's decline, and labor experts are not surprisingly split on the question on how much good marketing might do for unions.

Said Mr. Chaison: "The public perception of unions is down and a good argument can be made that regardless of what caused the decline, the fall might have been stopped or slowed if there were major advertising campaigns by unions."

Nelson Lichtenstein, labor historian at University of California at Santa Barbara, comes at it from another direction. "Do I think unions should do more advertising?" he asked. "No, I don't. They can never match money of their opponents or even liberal allies. The strength of unions, so far as they have strength, is personal and intimate. They mobilize their members [by] talking to people. Big ad buys are not at the top of the list of the most effective things that unions do."

Advertising, he added, is "not a magic device that's going to get them out of their terrible crisis."

Especially one that's outlasted the expiration date of a Twinkie.