A Ted Talk in my college town given by Erica Chenoweth.
Here is the WaPo’s Max Fisher writing about the topic.
Using violence also tends to reduce public support for an uprising. Chenoweth thinks this is because a violent uprising is more physically demanding and dangerous and thus scares off participants, but I’d add that violence is controversial and can engender sympathy for police and soldiers at the other end of dissidents’ rifles. A violent uprising can end up polarizing people in support of the government, whereas a government crackdown against a nonviolent uprising will often reduce public support for the regime.