Paul Krugman makes a fundamental point about the nature of the left-right divide:
One side of American politics considers the modern welfare state — a private-enterprise economy, but one in which society’s winners are taxed to pay for a social safety net — morally superior to the capitalism red in tooth and claw we had before the New Deal. It’s only right, this side believes, for the affluent to help the less fortunate.
The other side believes that people have a right to keep what they earn, and that taxing them to support others, no matter how needy, amounts to theft. That’s what lies behind the modern right’s fondness for violent rhetoric: many activists on the right really do see taxes and regulation as tyrannical impositions on their liberty.
There’s no middle ground between these views. One side saw health reform, with its subsidized extension of coverage to the uninsured, as fulfilling a moral imperative: wealthy nations, it believed, have an obligation to provide all their citizens with essential care. The other side saw the same reform as a moral outrage, an assault on the right of Americans to spend their money as they choose.
I've written about this a lot, especially in a review essay about the influence of Ayn Rand on the modern conservative movement and in another on Arthur Brooks. I think this is the essential issue in American politics. By that I don't mean it's the most important issue, though it is important. I mean it's the question that is driving most of the contemporary divide.