Campaigning is often done in phases and being able to filter people by historic support levels would be very useful. Currently, you can only see an individual's changes in support level in their activity feed. Filtering would give the ability to see trends across multiple people between specified dates. If someone is canvassed in 2010 as Weak Support and then in 2014 becomes Strong Support that is worth tracking and being able to search. Likewise, within a single campaign cycle, if someone is canvassed at the beginning as Strong Support and becomes Weak Support that is also important to be able to find out through filtering. Historic support levels tell a story and can also often tell us if their support was because it was a candidate canvass or because of other factors. People often give candidates different responses than general volunteers.