Ed Kilgore's got a good post on the "Who Lost the South?" debate that folks interested in the subject should probably read. I think his points lines up well with my argument that the Civil Rights Act destroyed the region's Democratic identification, but it's the culture clash and the Party ID, not the racial politics, which still hold us back years later.
The reason McGovern matters, though, is that 1968 and the McGovern convention really pounded that split home. It was right after Wallace had peeled off our supporters and suddenly we were running a guy who, for all his other attributes, struck this region as an alien life form. As Kilgore notes, Jimmy Carter provided a welcome interruption by being a Southern, religious, former naval officer, but his perceived wimpiness in the executive's chair ended up reinforcing our problems -- even when we run a tough guy, they'll govern like a scared child. Reagan, of course, codified the split in 1980, creating Reagan Democrats, who today are Bush's treasured white males. Anyway, you guys have heard this before. Kilgore's post is quite good, and you should read it.