As of this writing, Noah has posted five long columns on the topic, with more to come. You can find the first column here, links to subsequent columns appear on the first column. Be sure to check out his slide show of data tables with explanations, they are good.
As you might suspect, party politics are one of the explanatory variables considered. Inequality has increased more under Republican presidents than under Democrat presidents. I suspect Republicans, whether affluent or not, are substantially more comfortable with income inequality.
