Let me explain Dane county. I predict that Dane will be the center of all the attention, for several reasons.
To answer your question:
First: Check your chart, it doesn't look right. For Wisconsin, forget Ron Paul. The action is between Romney and Santorum. Please chart those and for consistency in the future, use the following colors: Romney (ugly green); Santorum (Dark Blue); Ron Paul (Red); Gingrich (Indigo or Turquoise, if you care to chart him)
Second:
a) There are 193 counties in Dane, and the average size in 109 and the median size is 88 votes. No flipping will occur with less than ~250 votes per precinct. (I need to do stats to find out exactly where the flipping starts)
b) There are only 14 precincts with votes > 250.
That's why the flipping does not always start at the same cumulative count on the X-Axis. If all the precincts were <250 votes (approximately) there would be no flipping at all. You have to look at the statistical distribution of the precinct counts.
Dane has some very odd irregularities that I am investigating. I'm looking at Madison, where Ron Paul did great. In one precinct 6 times better than Romney. This of course shoots down the theory that "Romney does better in big cities".
Next about Dane county, it is one of those counties, which uses a central tabulator by ES&S. This information will come handy later, I promise.