Nashville Post Politics
Pollster.com compares the current presidential race to the 2006 U.S. Senate race between Bob Corker and Harold Ford:
The differences between early deciders and late deciders are opposite of what we would expect if there was a race effect among late deciders. Whites who decided within the last week and a half of the campaign were actually 8% more likely to vote for Ford than those who made up their minds earlier. The same pattern held for less educated whites, rural whites, and whites living in eastern Tennessee. The only two groups where Ford did not do better among late deciders was for low income whites and older whites. But even in this case, Ford performed about as well as he did with early deciders, not significantly worse.
What does this mean for the presidential race? It depends on the extent to which you think the case of Tennessee in 2006 can be applied to the 2008 presidential contest. On one hand, the demography of Tennessee would seem to make it a good place to look for race effects among late deciders. On the other hand, electing someone to the Senate in a midterm election is a bit different from electing a president. But if you believe the comparison, then the experience from Tennessee in 2006 would suggest that there is little reason to expect late deciders to break against Obama because of his race.