Matt offers a slightly new view of the Republican "southern strategy":
It's true that the recent political success of the GOP has an enormous amount to do with the party's success in the white south, but I think the evidence strongly suggests that conservative politicians get the votes of white southerners precisely because white southerners like conservative positions on taxes, moral values, and national security. Southern Democratic politicians of the Jim Crow era, after all, mostly took conservative stances on all of these issues. The weird thing about Jim Crow politics is that white southerners with conservative views on taxes, moral values, and national security would vote for Democratic presidential candidates who didn't share their views. They did that as part of a strategy for maintaining white supremacy in the South.
And for a long time the strategy worked. Democratic politicians like Woodrow Wilson and Franklin Roosevelt loyally upheld white supremacy. The dam began to crack with Harry Truman, and then under Lyndon Johnson the national party decisively broke with this corrupt bargain. With that done, white southerners just took their conservative views on taxes and national security into the Republican Party where such views belonged. Racism is a key part of the story, but it plays a much bigger role in explaining why Adlai Stevenson and John Kennedy won South Carolina than in explaining why Ronald Reagan and George W. Bush won there.
I think Matt is obviously right that the South is not just conservative because they hate blacks . . . although it would be interesting to see how much the experience of Reconstruction altered Southern views of government.
The "Southern strategy" should imply not merely that Republicans started campaigning in the south (that would be logical if they thought they should win there . . . and would Paul Krugman really spurn white racist voters who supported, say, the Democrats on single payer?) It should imply that Republican policy changed to make it more palatable to racists. Is this true?