The rule in conventional democratic politics — followed rigorously for centuries — is to be as broad and vague about your ideals and desires as possible, so as to attract the largest possible base:
Consider the tea parties. What were they about? Their namesake — a thoroughly left-wing phenomenon, a mob of vandals who masked their faces like Hamas to ransack a private business whose only crime was obeying the law? A mood, a feeling, a thought? Maybe an agenda, if a negative agenda counts? No to healthcare reform? But not just no to healthcare reform…It was, and is, nowhere near clear. No surprise. The more people you get, the more powerful you feel. Unfortunately, if those people are milling about randomly in a “big tent” the size of Nebraska, you have accomplished very little in terms of coordinating support. You have not coordinated anything. All you have is a feeling. If you could get a million people behind some defined objective, you might be able to get that objective to happen.
But if the tea parties were promoting an actual manifesto, they would have had a much harder time recruiting. This would just have been weird. When you involve yourself in something like a tea party, you feel that you are contributing your thoughts, your ideas, your dreams, to a collective movement. This is the experience of conventional democratic politics. The last thing a democratic party wants to do is to crush those dreams, brutally, with its own.