The election I like to use as an example of racism helping the Democrats is Louisiana in 2003. If the Republicans ever run Jindal for President, and his Democratic opponent is white, I'll have no problem saying racism helped the Democrat get to 500 electoral votes, just like I have no problem saying racism helped Blanco in 2003.
Focusing on the 2003 election is a bit misleading. Although racism almost certainly did help Democrats in 2003 in north-central LA and the parishes north of Lake Pontchartrain (Republican strongholds), it did not help nearly as much as it helped Republicans in 1999 and 1995.
2007 GubernatorialBlanco(D) 51.95%
Jindal(R) 48.05%
Compare to 2002 Senate race:
Landrieu(D) 51.70%
Terrell(R) 48.30%
Now, Landrieu did have the advantage being the incumbent and Terrell being not a very good candidate, but you can see that the 2002 result between two "white" candidates was pretty similar to the 2007 result.
Compare to the two previous Gubernatorial elections, both involving black Democratic candidates:
1999Foster(R) 62.17%
Jefferson(D) 29.53%
1995Foster(R) 63.50%
Fields(D) 36.50%
And, of course, in 1991, the Republicans voted a known Grand Dragon of the KKK into the runoff election. Luckily, he had to go up against a popular, yet crooked, former governor in that runoff.
As you can see from the data, it is the Republicans who have benefited the most from racism in Louisiana in the last decade or two.
But my home state may be starting to turn the corner on its racist past. From last year:
2007Jindal(R) 54.29%
All other major candidates 44.62%
And he actually dominated those Republican stronghold parishes that he had lost in 2003.