South Carolina likes to pride itself on its "first in the South" status in the presidential primaries. And even likes to brag a little bit that they choose the candidate that goes on to be the nominee six out of the last six times. Is South Carolina really that in tune with the nation as a whole? Or is there a better explanation?
Let's look at their past results-
2008- John McCain won with 33% on January 19, where they and Nevada were the fourth and fifth states to hold primaries. It was the second state for McCain to win (he also took NH), and he was definitely not the frontrunner yet.
2004- George W Bush incumbent year
2000- George W. Bush won with 53% on February 19, and was 5th to hold a primary. He had already won in three other states by large margins.
1996- Bob Dole won with 45% on March 2, as the 9th to hold a primary or caucus. It was only the third state for him to win. But that was a "Super Tuesday" week where Dole won 11 more states over the next 4 days.
1992- George H.W. Bush won with 67% as a contested incumbent.
1988- George H. W. Bush won with 49% where they were 13th in the nation to vote, on March 5. He was tied at that point with Bob Dole. There was no clear front-runner until that day. Again, it was a Super Primary Week (Super Tuesday), and Bush won with large margins in 16 of 17 states that week.
1984- Reagan incumbent year
1980- Ronald Reagan won with 55%, and South Carolina voted 6th in the nation. Bush had won in 3 states, and Reagan only in 2. However, in the Super Primary/Super Tuesday week that followed, Reagan won in 5 of 5 states, and became the very clear front-runner.
So while South Carolina can brag that they picked the nominee six out of the last six times, it isn't really that miraculous. Only in 2008 did they vote early enough in the process that there wasn't a clear front-runner yet. In all other years there was already a set front-runner. There is no indication of any one year where South Carolina picked an upset for front-runner.