For example, of the 21 states that have the highest HDI (.95 and above), Barack Obama won all of them except Alaska. Of the 8 lowest scoring states--HDI of .849 and below, McCain won them all. For the 15 states in the second highest cohort (.900 to .949), Obama won 6. Of the 6 states in the middle of the continuum, Obama only won Florida. What we see is a strong correlation between a state's HDI and Obama's success there. All of his electoral votes came from states at the upper end of the continuum with the exception of Florida. McCain was only able to capture 3 electoral votes from the most developed states, aided by Sarah Palin's Alaska roots.
Mere coincidence??? Perhaps, but if we look at the recent trends we shouldn't be so surprised by this. Exit polling conducted on election day (and indeed during the primaries as well) showed that Obama and other Democrats had begun to make in-roads among those at the top of the economic ladder. We've similarly seen great movement away from the Republicans among the most highly educated. Thus, whereas traditionally it had been thought that the Republican base was among the high income/high education chunk of the electorate, this no longer seems true.
For more on this question of how class, education, and other variables are affecting voting trends, see Andrew Gelman's work.
***Update: Speaking of which, Gelman critiques and tweaks the numbers a bit here.
***Further update: After some more data critiquing, a re-scaling of the data and the following map. The electoral correlations I suggest still largely hold although Obama does better on the low, but not lowest, part of the continuum.