I think the Dems suck, are abject tools of capital - and the whole notion of their "spinelessness" arises from the fact that they are tools of capital who have occasionally to sound (and even act) like they're not. But they're not identical to the Republicans. In the 50s and 60s, both parties had liberal, moderate, and conservative wings. Since then, much of the Dems conservative wing became Republican, and the Republican party moved far to the right, becoming one of the most right-wing mainstream parties in the world. The Dems have accommodated that shift to some degree, but they're just not identical. Take a look at any of the liberal and conservative ratings systems (ADA, ACU) for some sample votes. Labor law, social spending, enviro protection civil rights, treatment of sexual minorities - quite different.
Even on this wiretapping bill, Dems voted overwhelmingly against.
[WS:] Another way of conceptualizing it is to divide issues into "discretionary" and "non-discretionary." The discretionary issues are ones whose outcome can be affected by the political standing of the party that controls the government. The non-discretionary issues are ones whose outcome is pretty much predetermined either by objective circumstances or by the firmly set balance of power in society, and thus are relatively independent of party politics.
Many of the issues for which Dems are blamed by self-styled radicals and populists are in the non-discretionary category. Clinton's welfare reform or death penalty are two examples. Both received broad public support, and thus their passage was virtually guaranteed, not matter what part was in power. The same holds for NAFTA and international trade issues. The only discretionary element was the extent to which these policies would be carried out - the Repugs would push it much further than the Dems did. Therefore, blaming the Dems for these policies is a classical example of a fallacy that attributed all effects to a singular cause even though multiple causes are at work. This was a favored canard of anti-communist rants attributing all problems of Eastern Europe to a single "cause" - the "evil communism."
I agree with Doug that Dems and Repugs differ quite substantially on discretionary issues, such as minimum wage, labor laws and occupational safety, social policy, military spending environmental protection, consumer protection, civil rights, urban development, cultural or educational policy. These are also the issues that matter the most in every day life situations for most people - which cannot be said about many non-discretionary issues such as NAFTA or death penalty.
Wojtek