SEOUL, South Korea — For months, the grieving parents of teenagers who drowned aboard the Sewol ferry have camped out on Seoul’s grandest boulevard, staging hunger strikes to protest what they call the government’s refusal to fully investigate the role that official incompetence and lax enforcement played in the disaster. And for months, the country mourned with them. The story of one father who subsisted for 46 days on water and salt gripped the nation.

But as the protests continued through the summer, helping bring the Parliament to a standstill, the president’s conservative supporters began a campaign of their own that would have been unthinkable in the early days of the disaster. Some groups publicly accused the families of holding the country hostage, and said they had shared enough in the grief. Others went so far as to pitch camp near the hunger strikers, taking selfies as they gorged on fried chicken, noodles and pizza.

While even some government supporters called the eat-in cruel, it was another sign that more than five months after the sinking that once united South Korea in sorrow, the disaster is polarizing the nation, splitting it along familiar liberal-conservative lines and threatening to derail President Park Geun-hye’s political agenda.

At the heart of the standoff is the parents’ deeply held belief that this is South Korea’s best chance to break the collusive ties between bureaucrats and businesses that are the seamy underside of the country’s economic rise — and which they believe were an underlying cause of the disaster. The only way to do so, the families say, is to fully investigate who bears responsibility for the sinking, no matter how high in the government the evidence leads.