This screen capture was taken Friday night, little before 7 pm central time.
The two graphs set the front runner as the whole and the other candidates as portions of that whole. No matter how many people are added, Obama and McCain stay as 100% of the available graph. But the more important issue is that it makes it look like Obama and McCain have the same amount of support, and that Hillary is way behind McCain. Thats part of the reason I started making my own graphs.
This graph is linked to the data on my google spreadsheet, it will update.This graph puts all six of the candidates that ABC/Facebook is tracking on the same scale. Its pretty clear how huge of a lead Obama has among the Facebook crowd. Its also clear that Hillary is actually ahead of McCain by about 35,000 people, but thats rather hard to see since the difference is much smaller relative to Obama's lead.
So when you see a graph, look for the scale and just because two bars look the same doesn't mean that they're the same value.