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Nike has severed its endorsement deal with Lance Armstrong. The cyclist also says he is stepping down as chair of the Livestrong cancer charity he founded. - 

Nike announced this morning it has severed its endorsement deal with Lance Armstrong. The cyclist also says he is stepping down as chair of the Livestrong cancer charity he founded. Armstrong says he doesn't want the doping allegations against him to distract from the organization's mission.

Scott Rosner, a professor of sports business at the University of Pennsylvania's Wharton School, is surprised at the speed of Nike's withdrawal given their pace with other similar revocations. Yet, Rosner notes that the doping allegations against Armstrong "really [go] to the integrity of the sport itself and the integrity of the brand -- that you are authentic, that you are a genuine athlete," which may have pushed Nike to act. 

Follow Jeff Horwich at @jeffhorwich