In the course of the 2008 Democratic presidential primaries, the most closely contested in decades, there emerged a demographic voting pattern.  Sen. Barack Obama appeared to do well in states with very large or very small black populations, but struggled in states with relatively more racial diversity.  One hypothesis is that racially diverse communities exhibit lower levels of trust, both within and among races (Putnam 2000).  Yet the apparent role of race might obscure the role of non-racial demographic factors that correlate with race such as unionization and education.  This paper estimates the relative roles of racial and non-racial factors determining the Obama/Clinton vote shares across states.