When he was in the Tour de France, Lance Armstrong was known for his incredible ability to get his bicycle up steep hills before most other riders.

Now, Armstrong faces another steep challenge: an onslaught of allegations by some past colleagues that he used performance-enhancing drugs to win the grueling race. Just to make the challenge even more difficult, a federal grand jury in Los Angeles has been investigating to see if any fraud was committed.

“It’s a whole series of concentric circles, and it certainly seems like the circles are closing in on Lance,” says Patrick Rishe, an economist at Webster University and director of Sportsimpacts, a sports research firm. “With all these people coming forward, you just have to wonder.”

The latest problem for Armstrong came Sunday, when CBS's "60 Minutes" aired an interview with Tyler Hamilton, a former Armstrong colleague on the United States Postal Service team who helped the Texan win the Tour an unprecedented seven times.

Hamilton claimed that Armstrong had failed a drug test in 2001 while competing in the Tour de Suisse, a race leading up to the Tour de France. But Armstrong was not worried about the failed test, claiming that the International Cycling Union (UCI) made the negative results go away, Hamilton said.

The UCI, in a statement Monday, denied the charge. “The allegations of Mr Tyler Hamilton are completely unfounded,” said the UCI. “The UCI can only confirm that Lance Armstrong has never been notified of a positive test result by any anti-doping laboratory.”

Last year, Floyd Landis, another of Armstrong’s former teammates, also made the claim that Armstrong had used performance-enhancing drugs. Five years ago, Frankie Andreu, another former USPS rider, told The New York Times that he himself used the blood booster EPO to help teammate Armstrong win the Tour.

Armstrong has long maintained there is no proof he used drugs and notes that he has passed hundreds of drug tests. He maintains that his accusers are liars.

"Tyler Hamilton is a confessed liar in search of a book deal – and he managed to dupe 60 Minutes, the CBS Evening News, and new anchor Scott Pelley,” wrote Mark Fabiani, Armstrong’s spokesman, on the website Facts4Lance.com. “Most people, though, will see this for exactly what it is: More washed-up cyclists talking trash for cash.”

Armstrong’s camp is doing more than issuing press releases. The former cyclist has lawyered-up. He has hired Washington, D.C., Patton Boggs attorney Robert Luskin, who defended Bush political adviser Karl Rove in the investigation surrounding the leak of a CIA officer’s name. In an interview with AM Law Daily, Mr. Luskin predicted that efforts by the US Justice Department to obtain Armstrong’s French drug tests would come up dry.

"I think what they're going to find in France is French fries and no evidence against Lance," Luskin told AM Law Daily on May 21.

Armstrong has much at stake. He is one of the most admired athletes, in part because he beat cancer in 1996 and return to racing. A year later, he formed the Lance Armstrong Foundation to help other people diagnosed with cancer. It has raised millions of dollars and is active today, especially for its Livestrong.org presence, an online resource for cancer survivors.

“You don’t want to tear down an icon,” says Dan Lebowitz, executive director of the Sport in Society center at Northeastern University in Boston. “He is someone who has stood for American values of overcoming great odds and obstacles and standing up for a cause that benefits many.”

However, if the allegations of illicit drug use are true, “We want to call him out on that issue, says Mr. Lebowitz. ”Cheating to get to the highest level is not commendable.”

A lot of money is at stake. Armstrong takes in about $20 million a year in endorsement money from companies such as Nike, Coca Cola, and Subaru, estimates Mr. Rishe. If Armstrong were to lose in a trial, Rishe says there is a “good chance” some of his sponsors would leave.

“It would depend on how deep the rabbit hole goes,” he says. “He might lose maybe 25 percent to 50 percent if he was ever outed.”