In the aftermath of the mass shooting at the Marjory Stoneman Douglas High School in Parkland, Fla. more than 20 companies have severed ties with America's most powerful gun lobby, as a wave of activism sweeps across corporate America. 

What’s compelling traditionally non-political businesses to participate in a very partisan boycott? 

Historian Nancy Koehn attributes the shift to "the incendiary octane power of social media," including the #banNRA movement on Twitter and Facebook, encouraging companies to take a stand against guns. 

"There has never been this amount of responsiveness in corporate America," Koehn said in an interview with Boston Public Radio Tuesday. "I have never seen anything like this." 

Apple, Amazon and other companies are now facing boycotts over their ties to the NRA. 

According to Koehn, companies are refusing to "take the heat over [an] association with an organization that's become very controversial."

Change won't happen overnight, Koehn says, likening the shift in gun popularity to the slow and steady cultural rejection of cigarettes, once a powerful lobby. "What happened to big tobacco, what happened to opioids," Koehn said, "it will happen to the gun manufacturers. Their place in society is now shifting." 

Nancy Koehn holds the James E. Robeson Chair of business administration at the Harvard Business School. Her latest book is "Forged in Crisis: The Power of Courageous Leadership in Turbulent Times."