The author of this quote, I believe, intended to point out that, for democracy to survive there has to be differences of opinion. In a democracy, it is the citizens who elect the people to represent them (Appleby, 1992). It is possible for several candidates to vie for a post; campaign and then leave the responsibility of voting to the body of citizens to be represented.
The fact that, in a democracy, more than one candidate may run for a position acknowledges that there may be more than one approach towards the representation of the group seeking to elect a representative (Benhabib, 1996). Hence, all candidates will have to put forward their independent views regarding how they see it best fit to represent the group. It is hence upon the group to determine which candidate presents the best strategy to handle the job bestowed upon him/her thereby voting for them.
This approach towards democracy has been successful in America. This came out clearly in the last general election where by the contestants took a different approach regarding the American soldiers in Iraq and The Health Care Reform. The delegates had to choose between the suggested polices. However, in some countries especially in Africa, many of the candidates do not endorse this aspect of differences as part of democracy. This has led to the formation of several coalition governments in the continent, which I think cannot function as per the expectations due to variance in their lines of action.
Many countries that have been under dictatorship rule, especially in the Middle East have decided to bring an end to this rule. This has led to several revolutions against governments of the involved countries, characterized by mass actions by the citizens of these countries who beg to differ with their leaders. These leaders advance to step down from office, set a date for a multi-party general election or both; and that is if they are not already thrown out of office.
All these situations clearly show that democracy brings out the strength existing in differences.