I wanted to have a go with d3.js and I had to choose some dataset to play with, so I decided to get the results of the first two elections of the Italina Democratic Party: 2007 and 2009. The data are from wikipedia and I have rewritten them in a json format and more technical info can be found on this post.
I have created two graphs:
In blue are plotted the result for the 2007 primary election, while in green are plotted the result for the 2009 primary election.
This is to show the amount of total votes in each primary election. It's clear that the second time less people have voted.