It's based on data from the Congressional Budget Office and the Center on Budget and Policy Priorities. Its significance is not partisan (who's "to blame" for the deficit) but intellectual. It demonstrates the utter incoherence of being very concerned about a structural federal deficit but ruling out of consideration the policy that was largest single contributor to that deficit, namely the Bush-era tax cuts.
The point of the chart really isn't partisan responsibility. It is the central role of those tax cuts in creating the deficit that is now the focus of such political attention. Call them the "Obama-Extended Tax Cuts" if you'd like: either way, a deficit plan that ignores them fails a basic logic, math, and coherence test.