In Winner-Take-All Politics, Hacker and Pierson, show how the two major political parties reacted over time to underlying changes in both the economics and politics of the US.
Contrast how the Democratic party reacted to those changes with how the Republican party reacted.
I think that Hacker and Pierson make this distinction between Democrats and Republicans fairly clear in suggesting that there is little distinction between both parties when it comes to economic policy. The Republicans represent what Hacker and Pierson call "Black Hats" while the Democrats represent "Gray Hats." The difference is that the former is fairly open and direct in their emphasis on policies that favor deregulation, private industry, maintaining the tax code's intrinsic inequality, and ensuring that the massive inequality of wealth remains as it has over the last 25 years. The "Gray Hats" Democrats are liberals on everything but economic policies. In this light, Hacker and Pierson suggest that on the issue of economic reform, there is little difference between both parties. When the American political dynamic moved "more centrist," it actually ended up embracing economic policies and practices that were more to the right, a politically philosophical approach that embraced more economic conservative policies that did more initiate the continued economic inequality that defined the modern setting. Examples of this would be Democratic leaders like Charles Schumer, who is a liberal on nearly every issue except for economic inequality reform, a pattern seen with "staunch" Democrats like Barbara Boxer, Dianne Feinstein, or Blanche Lincoln. In a setting where the nuanced and intricate dynamics of negotiating real change in economic policy designed to reduce the massive chasm of wealth inequality in America, the Democrats are more of Status Quo figures like their Republican counterparts. The primary difference would be that there is a clear distinction as to where the Republicans lie and a bit more obscurity on the Democratic position. For the most part, the authors conclude that the movement of the economic debate away from real and substantive progressive solutions that seek limit economic inequality has been abandoned by both parties, embracing an approach of ensuring that "the rich get richer" and that politics of the Status Quo remains, a setting in which political is not "bought" but rather "rented" from time to time.