Look at the county by county results. Some of Romney's highest support is on the other side of the mountains, and some of Santorum's highest support is in bordering counties. If you look at 2008 results, it's positively schizophrenic.
Nowhere have we seen 3 candidates getting 50+ percent in a county and finishing last in another different county.
If the mountain effect were at work, we'd expect to see what we saw in Michigan - heavily Romney on the coast, heavy Santorum in the interior.
Ohhh, I thought you were talking about general left-right polarization.
Yeah, about these caucus results, I got nothing, except that the caucus is probably somehow questionable in how it's run.