Obama takes bluer urban precincts, no correlation in burbs

I'm still puzzling through the interpretation of this, but I thought it worth sharing...

The graph shows the percentage of ballots in each Franklin County precinct that were cast in the Dem primary on the X-axis, and the percentage of votes in the Dem Primary in each precinct that went to Obama on the Y-axis.

The blue diamonds are precincts within the city of Columbus. The orange squares are precincts located in suburbs or townships in Franklin county.

Looking at the orange (suburban) squares, there is absolutely no relationship between the "bluenesss" of a precinct and the level of support for Obama. Looking at the blue (City) diamonds, there is a clear and striking relationship between the "blueness" of the precinct and the level of Obama support. In fact, 57% of the variance between urban precincts in support for Obama can be statistically explained by the percentage of voters participating in the Dem primary.