The shock of the revelations about the family lives of the Adamses and the Robinsons has hit especially hard because Northern Ireland remains a world apart from Britain and the Irish Republic, with their more laissez-faire social and sexual attitudes. With the recent decades of violence across the province entrenching many people in their faiths, Catholics and Protestants alike have hewed to the sterner moral codes of an earlier age. Politicians flouting those codes have done so at their peril.

Image Martin McGuinness shares power as the deputy first minister in Northern Ireland. Credit... Shaun Curry/A.F.P. — Getty Images

Last week, an emotional Mr. Robinson told reporters that he learned of his wife’s infidelity only on the night last March when she tried to commit suicide over the affair with the young man, who is now 21. But the sympathy he earned turned to demands for his resignation when a BBC documentary on Thursday revealed that Mrs. Robinson had taken $80,000 in secret loans from property developers to finance her lover’s investment in a cafe near Belfast, the province’s capital. Neither she nor her husband had reported the loans to the Belfast Assembly or the British Parliament, where the Robinsons each hold dual seats.

For now, Mr. Robinson’s survival as first minister depends on an investigation of the loan deal by an independent counsel, yet to be named, whose appointment Mr. Robinson promised Friday night. He said he learned of the loan several months ago, but did not know important details about it until he saw the BBC documentary. “I don’t believe that I have done anything wrong,” he added. When Mrs. Robinson went public last week with an acknowledgment of her affair, she announced that she will withdraw from public life and asked forgiveness of her husband and the public. “I am so, so sorry,” she said.

Her former lover, Kirk McCambley, now the successful co-owner of the cafe financed by the loans, has given a series of interviews saying the affair began when Mrs. Robinson befriended him after his father, who owned a butcher shop in the Belfast neighborhood where the Robinsons lived, died of cancer. “She was there to help,” he has said.

On Monday, political life will revive in earnest with the resumption of the fractious provincial Assembly at Stormont, the imposing neo-Classical-style Parliament building that sits high on a hill overlooking Belfast.

The issue of the transfer of police power has become deeply personal for the two men who lead the Belfast government: Mr. Robinson and Martin McGuinness, a former chief of staff of the Irish Republican Army, the paramilitary group that put its weapons away to support the government.

Mr. Robinson and Mr. McGuinness have made little secret of their personal dislike for each other. In a recent interview in Belfast, Mr. Robinson spoke of his disdain for the idea of handing power over the police to men who “bombed and butchered” their way to power, a formulation that sounded as though it had been crafted to refer to Mr. McGuinness, who started out as a butcher’s apprentice.