Despite the best of preparations and the fullest of precautions, every time a politician appears in public they take an enormous risk: encountering a real voter.

So it was for Prime Minister Malcolm Turnbull on Wednesday, who was beset by the dog-walking Raylene Mullins following an announcement in South Australia.

Proving that the township of Whyalla was never wiped off the map, Raylene confronted the PM about the government's free trade agenda and its impact on the local steelworks, her husband's employer.

"The produce is being ruined and nothing will help Australia if there's another world war because we wouldn't be able to exist," she said.