Support for the main opposition Law and Justice (PiS) party, from which Morawiecki's Development Plus grouping split, would fall to 15.9 percent, according to the survey by pollster IBRiS for the Wirtualna Polska news website.
The poll found that the governing Civic Coalition (KO) would win 28.5 percent of the vote, ahead of PiS on 15.9 percent, the far-right Confederation party on 13.5 percent, the ultranationalist Confederation of the Polish Crown (KKP) on 12.3 percent, the Left on 7.8 percent and Development Plus on 7.5 percent.
Compared with the previous IBRiS poll conducted in mid-June, support for the KO slipped by 0.5 percentage points, while PiS lost 3 points, state news agency PAP reported.
Confederation gained 1.5 points and the KKP rose by 1.4 points.
The centrist Polish People's Party (PSL) would receive 3.3 percent, below the 5 percent threshold required for parties to enter parliament.
The Razem (Together) party would win 1.9 percent, while the centre-right Poland 2050 group would receive 0.6 percent.
Some 8.7 percent of respondents said they were undecided.
According to seat projections published by Wirtualna Polska, such a result would give the KO 174 seats in the 460-member lower house of parliament.
PiS would secure 88 seats, followed by Confederation with 71, the KKP with 63, the Left with 33, and Development Plus with 31.
That would leave the KO and the Left with a combined 207 seats, short of a majority, while PiS, Development Plus, Confederation and the KKP together would hold 253 seats.
IBRiS also tested a scenario in which Development Plus did not contest the election.
In that case, the KO would receive 29.4 percent support, PiS 21.5 percent, Confederation 14.5 percent, the KKP 12 percent, and the Left 7.2 percent.
Under that scenario, PiS would be projected to win 123 seats, while the KO would secure 175. Confederation would take 76 seats, the KKP 59 and the Left 27.
Together, PiS and the two Confederation parties would command a projected majority of 258 seats, compared with a combined 202 for the KO and the Left.
The poll was conducted on July 24 and 25 using telephone and online interviews with a representative sample of 1,000 adults.
PiS has lost more than 30 lawmakers after they resigned their party membership amid an internal dispute, according to party leader Jarosław Kaczyński.
The dispute centres on a political association founded by Morawiecki, one of the party's most prominent figures.
Kaczyński said the party's leadership would meet on Tuesday to formally acknowledge the resignations.
The announcement followed a July 23 deadline for lawmakers to declare that they did not belong to any outside political associations or face expulsion from PiS.
The departures are the latest sign of growing internal tensions within the conservative party, which governed Poland from 2015 until losing power in the 2023 parliamentary election.
Morawiecki said on Friday he had refused to sign what he described as a party "loyalty declaration" and had offered to step down as one of PiS's deputy leaders.
(gs)
Source: PAP