CHICAGO (AdAge.com) -- Shortly after August Busch IV was named CEO of Anheuser-Busch, he accepted a company director's recommendation for a consulting firm that would assist with managing the brewer's burgeoning brand portfolio.

The firm, Cambridge Group, ended up going far beyond portfolio management. In fact, its exhaustive research resulted in the "Drinkability" campaign that -- four years and millions in fees later -- is considered a major factor in Bud Light posting the first full-year sales decline in its history.

The "Drinkability" debacle, however, resonates beyond A-B, as agencies increasingly chafe under the growing influence of consultants. Marketers are under pressure to justify their budgets, and CMOs, skating on ever-thinner ice, are trying to bring a more scientific approach to a discipline traditionally heavily reliant on gut calls. The degree to which these consultants' recommendations and findings can translate directly into creative is becoming a familiar frustration for agencies.

Consultants "can be outstanding at what they do, which is linear thinking and process," said Peter Krivkovich, CEO of independent Cramer-Krasselt. "It's just important for clients to remember that human behavior is not linear."

Management consultants popping up in marketing isn't exactly new. McKinsey & Co. has a huge and long-established marketing practice that's worked with Johnson & Johnson, Walmart and Procter & Gamble. Firms like Accenture and Boston Consulting Group do loads of work for Fortune 500 companies in areas such as consumer segmentation and marketing analytics. Chrysler recently asked the financial consultancy that steered it through Chapter 11, Alix Partners, to conduct its search for new ad agencies and even negotiate their compensation.

No 'turf war'
"What we're mostly asked to do is identify the root cause of the gap between a company's performance and aspirations," said Boston Consulting Group Partner Mary Egan. "That can be the product or the price ... or it can be the marketing message." She said Boston Consulting doesn't boast creative expertise nor does it have any interest in "starting a turf war" with creative agencies.

Executives at both Cambridge and A-B note that the consulting firm made recommendations that the brewer's executives were under no obligation to follow. But Cambridge's exhaustive findings led directly to dramatic shifts in how Budweiser and Bud Light were marketed. Each brand largely abandoned the emotional appeals that had helped them become the two largest beer brands in the U.S. for straightforward pitches about process and product attributes that coincided with worsening sales for both labels.

Some of its research was right on. The consultant was originally retained to help the brewer manage its portfolio, first by quantifying the entire alcohol-demand landscape and then by identifying where A-B's opportunities and challenges lay within it. This work helped shape the "megabrand" strategy for Bud Light, and led to both the successful rollout of Bud Light Lime as well as the less-impressive launch of Bud Light Golden Wheat.

"It was very helpful," said Keith Levy, A-B VP-marketing. "Marketing is a blend of art and science, and they helped us add more science into the equation."

Cambridge Group, a 30-year-old firm with sterling case studies for some of the largest consumer package-goods companies, seemed well-qualified to do that. Its CEO Rick Kash co-founded Spectra Marketing Systems, which sells a widely used system that predicts demand for every SKU in supermarkets.

'Insights'
In an interview, Mr. Kash stressed that Cambridge didn't touch creative, and that the campaigns that stemmed from the firm's findings were the result of decisions made by A-B executives and their ad agencies. "We rarely have anything to do with the creative process," he said, though he noted that occasionally the firm attends meetings with creative agencies.

Executives at the shops who worked on the "Drinkability" campaign -- DDB and Euro RSCG -- say it's true they didn't take orders from Cambridge. But they add that it seemed that executives at the brewery -- particularly Mr. Busch -- had invested so much time, money and energy into the process that its recommendations almost always quickly became the client's. Attempts to reach Mr. Busch for comment were not successful.

"It's just an enormous, expensive process, and clients buy in," said a former A-B agency exec. "But the insights weren't that insightful, and they really derailed [Bud Light]." In 2009, its shipments fell 2.5%, the first-ever negative sales year for the country's No. 1 beer.

"Drinkability" had been in fine print on Budweiser's label since the 1960s and often raised in creative briefings to communicate Bud Light's appeal: You could drink a lot of it, and it was less watery than Coors Light and less bitter than Miller Lite. Cambridge's process strongly endorsed it as the ideal rational benefit.

"If all you have is an emotional benefit, it can be duplicated," said Mr. Kash. "Great brands have both emotional and rational benefits." A-B execs refused to call "Drinkability" a mistake, but scrapped the campaign for this year's Super Bowl.