According to economists daron acemoglu and james robinson, democratization occurs in countries where there is a particular order of events in the struggle between ordinary citizens and elites. place the events in order from first to last

They argue the first event toward democratization is the threat of revolution, then creation of civil society organizations, and lastly an active middle class to provide moderation. 

When the citizens demand or threaten revolution, the elites must give up some power to maintain overall power. This is step one and is then up to the creation of organizations to enforce the elites come through with their promises. The middle class aids in providing education but also a vehicle for change. They are more moderate and will not allow the system to go to the extremes of the ordinary citizens or working classes. 

He gathered information from primary sources.