MANILA: Filipinos have scoffed and slurped to show their backing for Davao City Mayor Rodrigo Duterte ahead of next week's presidential elections.

The maverick mayor of the southern city is leading the "Gulp Poll" conducted by convenience store chain 7-Eleven, which has asked customers at their 1,650 outlets across the country to pick soda cups with images of their favourite presidential candidate.

The popularity of Duterte's blue cup has mirrored two opinion polls last week that put the 71-year-old between seven and 12 percentage points in front of his nearest rival, Grace Poe, ahead of the May 9 national vote.

"I picked Duterte because I want a change in society, and I see how well-received he is when he campaigns in other areas," said government employee Michael John Aguillon.

The store's poll, first won by President Benigno Aquino in 2010, has "undecided" cups in second with those of former interior minister Manuel Roxas, vice president and opposition leader Jejomar Binay, Senator Poe and Senator Miriam Santiago all trailing.

The convenience store is not the only ones to mix politics with the palate.

In downtown Manila, customers at Kamuning Bakery can pick a set of stuffed pandesal, a Filipino bread roll, named after a particular candidate.

Duterte's spicy pork sandwich was leading the race, bakery staff said.

"I saw most of the customers ordering 'Pan de Duterte' because they like the mayor of Davao, and the second most popular ever since we started was Senator Grace Poe," Kamuning bakery owner Wilson Lee Flores said.