You can't say there was no sustained attempt to keep the dissenters on board. All four rebels noted that they have been "under extreme pressure". Then again, that may mean that Ypsilanti and her supporters relied solely Schröder's and Müntefering's recipe for disacipline from the olden' days, mobbing. And yet again, I don't see a lot of other choices.
For example, I don't understand how anyone could have thought that giving Walter the economic ministry to keep him from rebelling was in the realm of the possible. This is the key post for one of Ypsilanti's key election themes, a potential saboteur there would just have killed her ambitious renewables program -- and especially Greens should see that.
Still, maybe more would have been possible. I have this crazy idea that maybe the big anti-communists could have been moved if Ypsilanti had them sit down for a long chat in small circle with van Ooyen & co. *Lunatic*, n. One whose delusions are out of fashion.
Parties remain competitors even if they cooperate. When party A makes a deal they need to know that party B will uphold their part. If the deal falls through party A needs to establish that it was party B's fault, so as not to be blamed by the voters. A vote for PES is a vote for EPP! A vote for EPP is a vote for PES! Support the coalition, vote EPP-PES in 2009!