I disagree
I think the democrats problems come from the fact that they are not unified
they are actually several differnet groups cobbled together
some are tree huggers, some are pro abortion, some are pro gay marriage and some are anti war
that is why kerry was such a flip flopper and no democrat can ever give a straight answer they always have to go through this huge mathematical equation to figure out what to say to piss off they fewest memebers of their patchwork base...
Yes, you are right that there are all these subgroups in the Dem party, and that there is a lack of unity, but IMO, one reason Dems don't give straight answers is that if they tell the truth, that they are leftists, many of them would be out of a job. Flip flopping is more a function of general dishonesty than principle, IMO, and happens with politicians of all stripes.
In any case, my point is that the Democrat Party is the party of the Left, and thus generally follows leftist principles, which are fairly well defined. Even if a good many of Dem voters don't seem to understand this. But the tree huggers, "anti war" folk (who aren't really anti war), "gay marriage" advocates, media and entertainment types, they are all united at least by being followers of leftist ideals. The individual issues still grow in one way or another from the fundamental principles of leftism.