Companies are already lining up to hand Phelps millions of dollars to associate himself with their products. He could soon be the face of a revamped and expanded swimming headquarters in North Baltimore. Some have even suggested that Hollywood snap him up to star as an aquatic superhero.
"I can't see any other story surpassing his," Dorfman said. "People just can't believe what he's been doing. There is a superhuman aspect to it. From that standpoint, he's hard to top."
Some marketing experts wonder if Phelps will remain hot during the long downtime between Olympics but for now, they say he has doubled his earning potential to at least $10 million a year and could become one of the richest Olympic endorsers in history.
Companies such as Visa, Speedo, Omega, Hilton and AT&T agree and have signed deals with the all-time leading gold medal winner. Visa had a new commercial, narrated by actor Morgan Freeman, ready to roll as soon as Phelps won his last race. AT&T's commercials, featuring a young woman as an obsessed "Phelps Phan," have been ubiquitous throughout the games.
Kellogg's will put Phelps' mug on Corn Flakes and Frosted Flakes, according to Access Hollywood. The swimmer's longtime agent, Peter Carlisle, told The Wall Street Journal that Phelps' Beijing performance will double his endorsement income and be worth an extra $100 million over his lifetime.
Phelps could certainly pull in eight figures over the next year, said Ryan Schinman, founder of New York City-based Platinum Rye Entertainment, which matches celebrity endorsers with Fortune 500 companies.
"Right now, the guy's got the world on a string," he said. "He's in that upper realm, not in terms of income but in terms of profile, with Tiger Woods and LeBron James and Lance Armstrong."
Phelps would be wise not to jump at every deal that comes his way, he said. Instead, the swimmer should expand and lengthen his existing deals with high-end companies such as Visa, AT&T and Speedo. Those companies must in turn come up with campaigns that burn Phelps into customers' minds for a long time to come.
He should capitalize now, Schinman said, because given the low profile of swimming, Phelps' feats could be out of the spotlight come football season.
One person who doesn't seem very interested in marketing questions is Phelps.
"If Bob [Bowman] and I were in it for the money, I think we'd be in a different sport," he said in Beijing. "I'm having fun at what I do, and I do it because I love it."
Even if money is secondary to Phelps, he has said he wants to change his sport. He hasn't clarified what that means, but if he were to fuel a swimming boom, he wouldn't be the first athlete to wield such power.
America went chess crazy in the mid-1970s after Bobby Fischer became world champion. A tennis boom followed the late-1970s exploits of Jimmy Connors, Chris Evert and John McEnroe. Even if such crazes didn't last, they made those competitors rich.
Marketers are taken with Phelps' regular-guy persona. In post-race interviews, he sounded confident and driven, yet a little taken aback by his achievements. People can imagine talking to him on the sidewalk, but place this aw-shucks character in the right context, and he's capable of otherworldly feats.
Nike used a similar formula to launch Michael Jordan to mega-stardom in the 1980s. He was a soft-spoken young man from a small city in North Carolina, but stick him in a pair of sneakers, show him a hoop and he could fly.
Phelps entered the Beijing games as one of the brightest stars in the Olympic firmament. Even without eight golds, he was projected to earn $5 million in endorsements this year and millions a year for the foreseeable future.
But Phelps was not one of the most famous athletes in the world, said Steven Levitt, whose company, Marketing Evaluations Inc., devises Q scores to measure celebrity appeal.
Only 39 percent of those polled in March were familiar with Phelps and, of those, 22 percent considered him a favorite performer, Levitt said. Tiger Woods, for example, was familiar to 89 percent of those polled and viewed favorably by 48 percent of that group. Levitt expects Phelps' numbers to rise dramatically in next spring's study.
By surpassing Mark Spitz, Phelps transcended sport in a way that few athletes ever do. His story headlined national news broadcasts for a week. Celebrity news publications and programs such as US Weekly, Inside Edition and TMZ.com have taken an interest in his personal life. One posting on the movie-geek Web site Ain't It Cool News said Phelps should look into playing Marvel Comics' superhero Sub- Mariner. "He is a man from Atlantis," gushed the site's creator, Harry Knowles.
On another Internet frontier, more than 1 million people have signed up to be fans at Facebook.
"He is much bigger than his sport," said Dorfman, who could see Dancing With the Stars coming after Phelps or MTV building a new reality program around him.
"It could be Michael Phelps teaching other celebrities to swim like Olympians or I don't know what," Dorfman said. "But he's at the level where I could see people imagining stuff like that around him."
Schinman agreed and said Phelps could try to use such platforms to boost participation in swimming. He said he could also imagine Phelps swimming in lucrative exhibitions around the world.
"Even people who don't normally care about swimming will want to watch him," he said.
Phelps could sustain his impact on swimming by buying and expanding the North Baltimore Aquatic Club's facility off Falls Road, said Howe Burch, executive vice president of Baltimore's TBC Advertising. Burch envisions something similar to Nick Bollettieri's famed tennis academy in Florida.
"From that perspective, the whole profile of swimming will be much higher than it has been," he said.
Phelps' road to marketing nirvana is not clear of obstacles.
Great as he is, his sport rarely engages the American public between Olympics. He'll never compete on television week after week, as Jordan did and Woods does.
Swimming has also never offered a wide launching pad for apparel sales. Kids could walk around in Jordan's Nikes. Well-paid adults can put on Woods' golf shirts and swing his clubs on the weekend. But it's hard to imagine regular folks throwing on Phelps' skin-tight LZR Racer suit to swim laps at the neighborhood pool.
In these respects, Phelps faces similar challenges to past Olympic giants such as Mary Lou Retton and Carl Lewis.
"His biggest downfall is that he's excelling in a sport that's not on the tip of everybody's tongue," Schinman said.
According to Levitt's studies, Phelps' familiarity fell from 54 percent in March 2005 to 49 percent the next two years to 39 percent this March.
"His achievement is greater than it was in '04, dramatically greater but we're still in the initial euphoria phase," Levitt said. "That's what gets the marketing people on board. The problem is once he gets past the talk shows and the SI cover, what's he going to do to maintain his connection to the public? That is an open question."
Retton was an endorsement darling coming out of the 1984 games. But with her competitive career essentially over and no sports apparel to hawk to a wide audience, her superstardom could not endure as Jordan's did. She's still a recognizable name who can earn good money from speaking engagements, but you don't see her in commercials.
That's not exactly bad news for Phelps, who will be able to stow millions now and earn a sizeable income from his athletics fame for decades to come, marketers said.
"I think in the worst case, he's able to make a very nice income from speaking engagements 20 to 25 years down the line," Dorfman said.
"But the nature of his sport will always be a challenge."
Sun reporters Hanah Cho and Rick Maese contributed to this article.
Phelps' sponsors, according to his agents at Octagon, which declined to specify the value of the deals:
Speedo USA: maker of swimsuits, a licensed brand of the Warnaco Group Inc.
Visa Inc.: credit card company
Omega: luxury watchmaker, a unit of Swatch Group AG
Hilton Hotels Corp.: hotel chain
PowerBar: nutrition bar from Swiss chocolate maker Nestle SA.
AT&T Inc.: communications provider
Kellogg Co.: maker of Frosted Flakes, Cheez-Its and Eggo waffles
Rosetta Stone Ltd.: language-learning software maker
PureSport: sports performance beverage, made by Human Performance Labs
SwimRoom.com: Internet site for swimmers
Source: Associated Press