Efforts to unite PASOK and To Potami, also by electing a single leader later this year, appeared to hit a wall Tuesday as the two sides exchanged accusations for the setback.
Officials from the two parties suggested that disagreements revolve around procedural issues as well as the political direction of the new project.
Potami has ruled out the idea of teaming up with a SYRIZA-Independent Greeks government.
Unnamed PASOK officials on Tuesday accused the party of Stavros Theodorakis of “foot-dragging” and “doublespeak.” In a statement Tuesday, the pro-business centrist party said that the leadership of PASOK seemed to be afraid of “clear procedures and transparency.”
A survey released earlier this week put PASOK on 5.5 percent while Potami was shown below the 3-percent threshold to enter Parliament.