At a time when new fees, protest movements and bad press are putting banks further on the defensive, can celebrity pitchmen help financial services companies soften their image?

Capital One is certainly trying, with an advertising campaign starring either Alec Baldwin or his wildly entertaining "30 Rock" character, Jack Donaghy—in these ads, it's hard to tell the difference—and another featuring the humor of Jimmy Fallon.

Norwegian bank DnB NOR has been experimenting as well. It recently captured huge buzz on both sides of the Atlantic with an ad that cast mega-watt movie star George Clooney, perhaps the most eligible bachelor on the planet, in the role of the adoring new husband of a surprised young woman. (The ad's tagline: "Some people are lucky in life...For the rest of us, saving up can be smart.")

There's nothing out there to suggest that Capital One can't find long-term marketing success with characters born after the Visigoth era, or that Norwegian bankers won't be able to maintain a relationship with the notoriously commitment-averse Clooney. But celebrity endorsements seem to work best when they're designed for the long haul, or when they play to an institution's specific strengths within a community.

Take TD Bank's successful marketing formula featuring celebrity endorsers Regis Philbin and Kelly Ripa. The morning television talk-show veterans came to TD Bank courtesy of Commerce Bancorp, which employed the duo prior to the firm's acquisition by TD Bank.

Maintaining the campaign helped smooth the merger for Commerce customers by carrying over brand recognition to the TD Bank name, according to Allegra Sandelli, senior vice president and director of marketing communications for TD Bank.

The six-years-and-counting relationship with Philbin and Ripa has "helped us stand out in a sea of sameness," Sandelli says. The pair was chosen initially, she says, for their "friendly, engaging and upbeat attitudes," with the hope that consumers would ascribe the same traits to the bank. It's a goal that has taken on new resonance since the start of the crisis.

So strong is the association now between TD Bank and its spokesman, the endorsement deal will continue despite Philbin's recent retirement from his talk show with Ripa, Sandelli says.

The value of a long-term relationship was a key consideration for Associated Bank of Green Bay, Wisc., when it signed Green Bay Packers quarterback Aaron Rodgers to an exclusive, multi-year endorsement deal last year.

Associated already had been affiliated with its hometown football team for a decade, and found that customers involved in the Packers affinity relationship tended to be better than average for the bank, says Nick Papachristou, director of corporate marketing for Associated. "As a result of that, and the momentum after the Packers won the Super Bowl, we decided to extend the relationship" with Rodgers, last year's Super Bowl MVP.

A recent study published in the Journal of Advertising Research found that product sales go up 4 percent on the heels of an endorsement from a famous athlete. And sales get an extra boost when that athlete has a major success—a Super Bowl or World Series win, for example—although the benefits diminish with each successive win.

Anita Elberse, an associate professor of business administration at Harvard Business School and one of the co-authors of the study, says she was surprised by the magnitude of the endorsements' effects. While her research focused on athletes, she says her "gut feeling is that there would be a positive effect from any celebrity endorser." But not everyone is on board with that notion.

Media tracker Ace Metrix, based in Los Angeles, conducted its own research on endorsements about a year ago, studying more than 2,600 ads. Peter Daboll, CEO of Ace Metrix, says that across various industries there were only a few cases where celebrity ads outperformed those that do not feature stars, and the advantage was never large enough to offset the fees typically paid to the celebrities.

Ultimately, whether a company uses celebrities in their ads may be less important than how they use them. Maintaining a long-term affiliation, for example, will likely produce better results than a celebrity-studded ad meant to shock and awe consumers into a response.

"It's important that we've maintained a consistent relationship for years" with Philbin and Ripa, TD's Sandelli says. "This is not about shock value, but the continuity of the brand."

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