Not technically difficult but incredibly tedious. First, you have to go out and collect it from all 50 Secretaries of State, and in come cases county officials. Some states send you the data on a CD (no joke). You then have to clean the data, which is often not in great shape, and then normalize it.<p>Even then, you only have a snapshot, because the states typically don&#x27;t keep historical data. What this means is that your dataset won&#x27;t be as good as someone who&#x27;s been collecting this data for years, and thereby knows things you won&#x27;t like where someone used to live, how often they voted there, who recently dropped off the registered voter rolls, etc.<p>In this case, even this data wouldn&#x27;t be enough, because the Sanders team had made likely hundreds of thousands of contacts with voters, and recorded what issues they cared about and who they planned to vote for. This data, which they personally collected, is now inaccessible to them.<p>edit: expounded