From the exit polling, we see that 24 percent of South Carolina Republicans cited illegal immigration as the most important issue in this election. Among those, McCain placed second with 24 percent.
This means that a ceiling of 18 percent of the most dedicated Republican voters in that conservative state cared so much about illegal immigration that they voted against McCain. Another six percent cared about it so much that they voted for him. That puts McCain’s immigration deficit in the South Carolina GOP primary at 12 points overall — if you accept the idea that immigration-minded voters perceived all other candidates (including Huckabee) to be more hawkish on immigration than McCain.
I think that’s a lot less than most people would expect. The exit polls from New Hampshire told roughly the same story.