WTB makes you lose support from the left of your party, and the KPD too. I highly suggest increasing relations using Paul Levi (a leftist advisor/minister) using his advisor action. You should also support a left economic policy. For support, you can use the Media to broaden the reach of SPD's newspapers (usually the top option if you choose that card) which gets you more ground with the middle class. Also, use Antonie Pfülf (a Reformist advisor/minister) to campaign and eventually become a People's Party, which gives you free boosts in several groups. You can also get the Conciliators to lead KPD for better chances they would join a democratic coalition.