There's an interesting debate under way as to whether or not Democrats have "gotten more liberal" over the past 10-15 years that I think is hard to understand without first taking as background the basic long-term fiscal problem facing the United States.
The way this goes is that for a long time now we've been committed to providing health care services to the elderly, the disabled, and the poor and also to bolstering the general incomes of elderly people. Maintaining these commitments is projected to grow considerably more expensive in the future. Consequently, thanks to baseline games everyone thinks they're wise and moderate and everyone else is crazy. Start with Paul Ryan and his acolytes. Ryan's basic view is that all he's trying to do is ensure that the federal government's spending is brought in line with historic norms about the level of taxation. He's a conservative, to be sure, and this agenda is clearly animated by a belief that high taxes are bad. But far from a radical effort to scale back the welfare state, it's a sensible effort to preserve the status quo. On the other hand, serious liberals say all they're trying to do is to preserve America's historic social safety net. Social Security, Medicare, and Medicaid are all longstanding politically popular programs that are effective at achieving their program calls and appear to do so in a cost-effective manner. Obviously it's liberal to say that maintaining these historic achievements of American liberalism is important, but it's hardly radical to simply insist that we not shred effective and popular programs. But then you have the hazy Obama/Simpson-Bowlesish center that wants to raise taxes and cut programs. What could be more sensible? This is the very definition of sober-minded centrism. You have two divergent lines so you need to pick a path in the middle. Except a large bloc of radicalized conservatives and a smaller-but-not-trivial bloc of radicalized liberals are preventing all progress. It's madness!
Now I have my own views about all of this. But I do think it's worth taking a deep breath and trying a little bit to empathize with the different perspectives. The issue isn't so much that they all have equal merit, but they do I think all have equal claim to be a kind of sensible defense of the status quo against radical alternatives.