Let's start with a small hommage to The Man and his moment of genius. He has shown that in Anderson, SC and Greenville, SC, there is an apparent 1-to-1 vote flip between Romney and Paul. It is spectacular because the result is that Romney and Paul actual swap their final score!
Here are the 2 counties using my representation. It is totally mathematically equivalent to The Man's original work. The very same data from another angle.
On those chart, a 1-to-1 vote flip which ends up as a final score swap is very easy to detect. You want to see a cross between 2 candidates, and final candidates' scores at 100% equal to what they are on the left part of the chart. In Anderson, Romney scores at 100% is Paul's at 10%, and vice versa.
Notice as well that what The Man's plotted rightly as the fit-to-trend scores of Gingrich and Santorum become simply dead flat line on those charts. And boy, are they dead flat! "Natural", to be expected/predicted flatlines...
Now do those 1-to-1+final score swap crosses happen a lot? No. A quick perusal reveals another one in Greenwood and that's about it. Out of 47 counties. So flipping votes is the goal, complete score swap looks like a collateral, unintended coincidence.