Nike Inc, the world's largest sportswear maker, top beer maker Anheuser-Busch InBev and sunglass maker Oakley, owned by Luxottica, all said they would stand by the 40-year-old American, who on Friday lost his record seven Tour de France wins after he decided to stop fighting USADA charges that he used performance-enhancing drugs.
"Lance has stated his innocence and has been unwavering on this position. Nike plans to continue to support Lance and the Lance Armstrong Foundation, a foundation that Lance created to serve cancer survivors," Nike said in a statement.
Other sponsors including Trek Bicycle Corp, a leading bike maker, and 24 Hour Fitness, which operates fitness clubs, said they were monitoring the situation.
Texas-born Armstrong has been one of the most successful and polarizing cyclists of all time, surviving testicular cancer to win the Tour de France an unprecedented seven times from 1999 to 2005. He has become a prominent advocate for cancer research and awareness through the Lance Armstrong Foundation and Livestrong mission.
But Armstrong has also been fighting allegations that he had doped throughout his career. He maintained his innocence in a statement on Thursday, but said he no longer had the stomach to contest the USADA's charges, saying "enough is enough."
Robert Boland, professor of sports management at New York University, said Armstrong's extensive work on cancer has made him a hero to many, and will help blunt the impact of the doping allegations.
Livestrong has raised over $470 million for cancer research, in part through the sale of its yellow wristband that became a global phenomenon with over 84 million bands distributed.
"His story has not been diminished. Here's a guy who essentially was at death's door with cancer and came back. That example still makes him very compelling," Boland said.
Still, Boland said it would be difficult for Armstrong to continue to endorse bicycles or bicycle equipment, since he has now been banned from competitions.
"If he can't show up at certain events, how do you use him?"
Armstrong's net worth has been estimated at roughly $125 million. According to Forbes magazine, he earns more than $10 million a year in speaking fees and endorsement deals.
Any impact on his earning potential is mitigated by the fact that Armstrong is retired - he last participated in the Tour de France in 2010 - unlike Tiger Woods who almost three years ago faced scandal when he was at the height of his golf powers.
But retired athletes can still rake in millions from a robust calendar of speaking engagements, such as giving a keynote speech at a trade show.
Armstrong earns $150,000 per speaking engagement and that he does about twenty per year, according to his agent, Bill Stapleton, who predicted that Armstrong will remain "incredibly marketable" because his fans will stay loyal.
"I think if we talked in five years, he'll still be making speeches, he'll still have his sponsors, and his foundation will have made over a billion dollars," Stapleton told Reuters.
Indeed, the Lance Armstrong Foundation said that it had seen a 30 percent spike in donations on Friday, and that the nonprofit group had seen an outpouring of support for the cyclist.
SportsOneSource analyst Matt Powell said some sponsors might downplay Armstrong for a little while but that as long as he is not actually proven to have taken drugs, they should resume.
"I don't think it will affect his sponsors unless at some point it's proven that he's taken drugs," Powell said.
AB InBev said Armstrong would continue to be a spokesman for its beer, Michelob Ultra.
"He has inspired millions with his athletic achievement and his commitment to helping cancer survivors and their families," said Paul Chibe, vice president of US marketing.
Armstrong is also co-owner of Honey Stinger, a maker of energy bars and gels based in Steamboat Springs, Colorado. The company said it will continue working with him and will continue to support the Lance Armstrong Foundation.
There was no immediate comment from Armstrong's other corporate sponsors, including RadioShack and exercise bike maker Johnson Health Tech.
George Belch, a founder of San Diego State University's Sports Business MBA program, said Armstrong was less of a draw for major advertisers since his retirement.
"I don't see the Fortune 500 companies knocking on his door anymore," Belch said, though he guessed that Armstrong would continue to be attractive to smaller brands.
Armstrong signed a three-year deal with Michelob in October 2009. The company said it was sticking by Armstrong but did not say whether it would renew the relationship.