[WS:] My point, exactly. However, there is one more point that is crucial, but that tends to be neglected. As I see it, you need a three-tier structure for successful socialist/labor mobilization, so to speak. The first tier is the economic base, which entails economic organizations engaged in significant economic activity and controls significant economic resources. This would be equivalent to the corporate sector - by itself it is not political but it is in a position to contribute significant economic resources to the political process and employ enough people whose economic interests are clearly tied to it. At the second tier is a "mass" political party - a party complete with media and think tanks that represents the political interests of the base in the routine political process and mobilizes wide popular support. This would be a mainstream labor, social democratic or socialist party that can attract at least 20-25 million loyal voters (i.e. those consistently voting for that party platform) in a country of the size of the Etats Unis (ca. 133 million voters in the last presidential election), and whose goal is to put pro-labor or socialist issues on the mainstream political agenda and get elected pro-labor and socialist candidates to political offices at all levels of government (locals state and federal). The third tier is a vanguard party whose main role is to act as "commandos" in political battles - to take advance positions (way to the left of the mainstream socialist or labor party) and to launch fierce attacks on political opponents (something akin to the Tea Party or even MoveOn.org). Both the second and the third tier can effectively exist only if they receive adequate material support from the base - in terms of economic and human resources.
As I see, most of the discussion concentrates on the third tier and sometimes on the second tier (as your example of Die Linke seems to suggest), but the first tier - the material base - is almost universally neglected. I see it as a remnant of old Marxist thinking about the role of the proletariat as a unified socio-economic class created by capitalism and ready to be mobilized for a revolutionary cause by political parties (mass or vanguard.) That assumption might have been valid at the turn of the 20th century but certainly not today. Hence the need for creating the material base before any successful mobilization is possible.