Younger whites vote that differently from older whites in SC? In many conservative states they vote more GOP in general than the olds, such as in Kansas. Youngs in Kansas are very serious about Jesus - yes they are - and the moral rot corroding away America's virtu.
From what I can tell, there's really not much of an age gap in Southern Whites (or Southerners in general actually) like there is in say, California. McCain actually won the 18-29 SC White vote by slightly more than the overall white vote (mostly because Gen X is abnormally Democrat). Democrats do better with the Youth in those states because it's significantly blacker/browner than other generations (how much of this is Obamamania turnout though I don't know since I'm using 2008 numbers). In 2008, the 18-29 Turnout in SC was barely 50% white while the 45-64 was about 75% White. Obama won the former age group by 10 points and lost the latter by 22.
Obama even did only 3% better than the White vote average in Virginia and Florida, both where much of the population is decidedly
not southern. The only "Southern" states where there was a big age gap in white voters were North Carolina (where Obama won the young by 12 despite losing the rest of them by about 35), and Tennessee (where Obama lost young whites by 8 and lost the rest of them by 30)
If you measure for Congressional Races rather than the presidential, it gets weirder still. In 2008 Texas, Cornyn did 6 points
worse with the white 18-29s than the white overall, but actually managed to do 5 points
better with Young Hispanics than with Hispanics overall, which is why he won the minority white 18-29 Demographic in the State.