The opposition Civic Platform (PO) party came in second with 17 percent support, 1 percentage point more than in the previous poll in early August.
Support for the opposition Nowoczesna party grew by 4 percentage points to 16 percent.
The Kukiz'15 group was supported by 6 percent of respondents, down by 2 percentage points from the previous poll.
Other parties would not win parliamentary seats as they fell short of the required 5-percent threshold.
Sixty-six percent of respondents declared they would go to the polls if elections were held in early September.
CBOS carried out the survey on a representative sample of 981 adult respondents on September 8-15. (PAP)
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