Pacquiao's standing dropped after he said that same-sex couples were "worse than animals" in an interview with a local television network, according to the poll by Pulse Asia Inc, one of three major survey companies.
The percentage of people who said they would vote for Pacquiao dropped to 34.8 per cent in the February survey, which questioned voters from February 15-30, down from 46.9 per cent in the previous survey.
The 37-year-old, eight-division boxing champion apologised on February 16 following a backlash against the comments, which prompted sports company Nike to stop his sponsorship deal.
Television network Home Box Office has also condemned his statements but said it would not cancel a pay-per-vew showing of Pacquiao's fight with American boxer Timothy Bradley on April 9.
In the latest Pulse Asia survey, Vice President Jejomar Binay and Senator Grace Poe were in a dead heat in the presidential race, with 25 per cent and 26 per cent of voters, respectively.
More than 18,000 positions are up for grabs in the May 9 general elections, including national, regional and local posts.
- DPA