Thanks to some help from a very dedicated friend, I was able to get the poll results for the Pikachu vs. Cloud match once every hour for the duration of the poll. This info should give us an idea of the typical vote distribution for each poll over the course of the day. So if you ever wanted to know what time most of the votes come in, now you'll have a pretty good idea. All times are in CST.
Additionally, you can see a detailed analysis of the poll results for the tournament final at King Morgoth's site (that information will also appear on this page in the near future).
The black line is the one we're really interested in here, the others are just for interest's sake. As you can see, the biggest spurt of voting comes immediately after the poll opens, then declines sharply to its lowest point in the early AM. Votes then increase in frequency at dawn and peak around noon (with a mysterious blip around lunch time), before gradually declining for the rest of the day.
This graph shows the percentage of the hourly votes that each character was receiving. It does not show the overall percentages, just the percentage for each specific hour. This allows us to see how popular each character was at different points during the day. It has been suggested that the votes of a character like Pikachu might jump during the early morning hours when it is suspected kids will be waking up and voting. However, this graph shows that Pikachu was just as popular during the early AM when the kids should be asleep as during the morning. That would seem to disprove the theory, although it is true that Cloud gains in popularity as the day progresses. By the late evening Cloud is receiving his highest percentage of the incoming votes for the entire day. So you can draw your own conclusions (there's certainly no noticeable spike).
This graph shows the size of Cloud's lead over Pikachu throughout the day (Cloud's percentage minus Pikachu's percentage). From this you can see how the overall vote percentages changed as the day wore on. It seems that after getting off to a rough start (ignoring the initial spike), Pikachu began to cut into Cloud's lead (percentage wise) until about 10AM, at which point Cloud began to take over. From that point on Cloud continued to widen the percentage gap, reaching an over 59% lead. He was never really threatened by Pikachu, and he maintained at least a 55% lead throughout the day (78% Cloud to 22% Pikachu at its closest).