Germany SPD: An even bigger change than Labour would need. The SPD must reconnect with its true social democratic values, and commit to reversing the Agenda 2010 laws, and raising the taxes on the wealthy to the 53% rate that existed before Schroder cut them, possibly even higher. And this is impossible with the SPD as it currently is. So, most of the Seeheimer Kreis and Netwerk Berlin factions will have to leave and start a new, centrist party that could become the CDU's new natural coalition partner. Then, the faction of die Linke that came from the SPD could rejoin it. Everyone wins! Except die Linke, but they've been on the verge of splitting for a while. But overall, all of this is about as likely to happen as Texas is to legalize gay marriage.
Far less so. The Seeheimer Kreis would serve no purpose whatsoever if they weren't in the SPD.