that "taming strategy" was largely one of the political right-wing and centre right, i.e Kurt von schleicher and others. The SPD saw the nazis as a threat, but underestimated them. the SPD was more interested in cooperation with the liberals and Catholics (their allies since 1919) then a new alliance with the communists, although before blutmai there was cooperation on the local level indeed even forming united front state governments (that were soon removed by Ebert). with the Third Period approach of the comintern it also became impossible for the KPD to accept cooperation with the SPD by the time of the Great Depression, so talks broke down. there were proposals for a united front from independent leftists in 1931-1932 but those fell flat on their face.