The survey conducted by ProRata on behalf of Efimerida ton Syntakton ("Newspaper of Editors") newspaper shows Syriza leading ND at 23 percent versus 19.5 percent.
At least 25.5 percent of those polled were undecided.
A July survey placed Syriza ahead of ND by a wider margin with 26 percent of support versus 15 percent for ND.
The drop in numbers follow Tsipras’ about-face toward the latest, third in the past five years, bailout package agreed on by Greece’s international creditors. The 86-billion-euro ($96.8 billion at current exchange rates) assistance is contingent on Athens accepting painful economic reforms and austerity measures.
The former prime minister announced snap parliamentary elections in hopes of gaining enough backing for the bailout.
Supreme Court judge Vassiliki Thamou was appointed caretaker prime minister and is expected to be sworn into office later on Friday before the elections.
Former Energy Minister Panagiotis Lafazanis leads a newly formed Popular Unity party made of 25 breakaway Syriza lawmakers who continue to reject the bailout deal. The party has 3.5 percent support in the ProRata survey, thus passing the 3-percent parliamentary threshold.