Had Hitler not been made Chancellor, odds are in the next election as the economy picked up the SDP, Centre, and BVP would all have made sufficient gains to form a coalition government.
Meanwhile, the issues between Hitler and Strasser were becoming more apparent. Strasser was contemplating taking his folks and splitting off from the NSDAP to form a National Socialist Freedom Party that would coalesce with the SPD (the SPD opted against this historically).
So what if a grand coalition had formed under Otto Wels, the Nazi Party split between the Hitlerites and the Strasserites, and the Weimar Republic continued on?