WASHINGTON -- After a dominating political victory, as in 2008, the expectations of a party's most ideological elements are raised. With sufficient boldness, and sufficient ruthlessness, anything seems possible.

But the American two-party system has a self-correcting mechanism that is Madisonian in its balance and elegance. A party becomes more dominant by becoming more diverse. Losing parties shrink toward their ideological core, as Republicans have done. Winning parties expand to encompass more of the ideological center, the undeniable Obama achievement. But this places centrists in positions of legislative influence, which enrages activists who feel the moment for ambition has finally arrived.

Thus the current health care debate taking place largely within Democratic ranks.

Democrats begin as the more diverse of the two main political parties. About 38 percent of Democrats consider themselves liberal, 40 percent moderate and 22 percent conservative. By way of contrast, 73 percent of Republicans describe themselves as conservative. A Democratic majority is already a coalition. And recently added Democratic legislators have tended to win in purplish portions of the country.

It is among moderate and conservative Democrats, along with independents, that concerns about spending and the deficit are rising sharply. In March, Democrats of every ideological brand overwhelmingly believed more spending was essential to improve the economy. Now 48 percent of moderate and conservative Democrats put a greater priority on cutting spending to lower the deficit -- a view shared by 56 percent of independents.

So how are these moderate elements being treated by the Democratic establishment? For the most part, with contempt. Liberal interest groups, and even the Democratic National Committee, are running ads targeting Democrats with moderate views on health reform. It is the Chicago-style, political hardball that some political operatives imagine is sophisticated but is often counterproductive. Do Sens. Evan Bayh, Mary Landrieu and Ben Nelson really need to be lectured by the left of their party on the interests and views of their own constituents? Continued...