Visualising changes in many-to-one (directional) relationships (votes) between a set of objects over time

I have a set of objects, each of which can be assigned to another object within the set in a many-to-one, directional assignment, like a vote. Objects cannot be assigned to themselves reflexively, but they can be in an unassigned state ("not voting"). So for example, the set {A, ..., Z} plus relation could be in the following state:

A -> E
E -> C
B -> C
C -> B
D -> Y
{F, ..., Z} are not voting.

This state will change over time, in discrete steps, one vote at a time. For example, at time t = 0 the set could be as above. Then at t = 1, Z votes for C (Z -> C), resulting in the state:

A -> E
E -> C
B -> C
C -> B
D -> Y
Z -> C
{F, ..., Y} are unassigned.

Can anyone come up with a neat way to illustrate graphically this set and the state changes over time? Ideally, it should be evident at a glance

• How many votes there are for one object at a given time.
• Which objects are voting for another given object.

Thanks!

• How many objects will be in the set? How many objects will receive votes, how many will receive a considerable amount of votes? Are votes eternal, or can they be retracted or changed? – dobiwan Sep 13 '14 at 12:01
• There will generally only be between 10 and 50 objects in the set. Any object can be voted for, but the number of votes is obviously limited to the number of objects (1 vote per). Votes can be retracted and changed. – ouroboros Sep 15 '14 at 7:48  