When you say a SPD-LP-Green coalition is impossible is that because of the numbers or due to resistance within the SPD and the Greens? I think that even if it got a slight majority it would still be impossible due to the strong hostility of many within the SPD and Greens to the LP and vice versa.
As for the non-PR element, 2002 was an exception when it didn't play that much of the role - with the SPD's sweep in the East balancing the CDU/CSU's sweeps in the South. You probably recall Unionist complaints on election night that the non-PR aspect stole them the victory as largest party, complaints that proved premature with an end result showing SPD just slightly ahead on list votes. (The SPD's advantage was just 3 seats.)
This year however, (I think jandsm gave us a link I regrettably lost) projections show no SPD direct mandate sweep anywhere, but a CDU one all across the South and central West. *Lunatic*, n. One whose delusions are out of fashion.
