Governing PRI gained four percentage points while National Action Party lost four.
The relatively new left-wing party Morena continues to hold on to first place in a new poll in which voters were asked which party they would vote for if a presidential election were held the day of the survey.
According to a El Universal newspaper report cited by mexiconewsdaily.com, Morena dropped a point to 23% while the National Action Party lost ground, dropping four points to 19%. The governing Institutional Revolutionary Party (PRI), on the other hand, moved up four points to 16%.
The Democratic Revolution Party dropped from 7% to 6%.
The poll was conducted through face-to-face interviews with 1,000 adults between August 10 and 17 by the newspaper El Universal and the polling firm Buendía&Laredo. The comparisons are from the previous poll, conducted in May.
The PRI also made some gains among its strongest opponents.
Last May, 50% said they would never vote for the party. Some have since changed their minds because the percentage declined to 41% in the latest survey.
Morena lost points for that particular question, polling 14% this time around, compared to 10% in May.
For most, the worst outcome of the 2018 presidential election would be a PRI win. Fifty-two per cent echoed that sentiment, while only 32% feared a victory by Morena and its firebrand leader Andrés Manuel López Obrador.
The election will be held July 1, 2018. Voters will also elect a new federal Congress.