|Source: The Atlantic|
The author offers a note of worthwhile explanation for the most correlative measure, the McCain vote share in 2008:
What about politics? It's hard to quantify political rhetoric, but we can distinguish blue from red states. Taking the voting patterns from the 2008 presidential election, we found a striking pattern: Firearm-related deaths were positively associated with states that voted for McCain (.66) and negatively associated with states that voted for Obama (-.66). Though this association is likely to infuriate many people, the statistics are unmistakable. Partisan affiliations alone cannot explain them; most likely they stem from two broader, underlying factors - the economic and employment makeup of the states and their policies toward guns and gun ownership.I think we're going to see this graph a lot in the upcoming gun control debate.