New Obama support graphs

Following up on my post on where Obama is winning and losing, here are some updated graphs breaking down his support at the state level.

First, here's a plot of a flexible polynomial fitted to state two-candidate vote totals by date -- you can see the upward trajectory in Obama's support levels, though the line weights each point equally:

In a linear regression, the strongest predictors of Obama's overall support are whether it's a caucus (+), Democratic presidential vote (-), and black population (+). Here's the plot of presidential vote, which indicates that Obama does worse in heavily Democratic states (the fitted line excludes the outlier of Washington, DC):

By contrast, Obama does better in states with larger numbers of African Americans, though the trend is concentrated among primary states (the linear fit is only for those states):

State education levels (specifically, the proportion of the population with a college degree) are also somewhat positively correlated with Obama support:

Finally, the strongest predictor of Obama's white support is the number of Southern Baptists in the state (-), which has been suggested as a measurable proxy for "Southernness":

Out of sample predictions from a model like this are likely to be highly inaccurate, but for what little it's worth, a regression of Obama support on black population, Hispanic population, state population (logged), 2004 Democratic presidential vote, a dummy variable for whether the state has a caucus, proportion college graduates, and Southern Baptist population predicts narrow losses for Obama in PA (48%) and OH (49%) but a big win in Texas (66%).

Comments

[Jinchi]

I'm just eyeballing your plots here, but it seems like "Obama support by Democratic presidential vote" is pretty much flat for primary states (even excluding DC).

Similarly, you see a trend in "Obama support by state education" - but again it looks pretty flat for primary states (excluding DC), strongly positive for caucuses.

I think you're contaminating your sample here. After all, you've already demonstrated that there's a big separation between caucus and primary election results.

[T_Porter]

Brendan,

Given that Obama seems to improve in a state the more he campaigns, does/should that diminish the weight of the Super Tuesday data, or at least impact our interpretation of them? For example, if they re-held Massachusetts today would the numbers be the same? And would does that tell your analysis?

(forgive weak logic: I am not a wonk)

Keep up the good work, Brendan!

[Ben]

Thanks for these analyses Brendan. I don't deal with data like these much, but I had two questions.

1) You exclude IL, AR, and NY. Perhaps HI and KS should be excluded for similar reasons?

2) Picking up on T_Porter's point, I wonder if there are publicly-available data you might add to your model to factor in the effect of time a candidate spends in a state in the month prior to the vote?

A model with a factor for money spent on advertising would be interesting too, but I wonder where you could possibly get such data.