In the long and turbulent history of populist movements testing the boundaries of democratic norms, Britain's Reform Party now finds itself at a consequential crossroads. Two of Nigel Farage's most trusted lieutenants resigned Friday after a Channel 4 undercover investigation alleged they had arranged illegal foreign donations and undisclosed political polling, placing the party under the gaze of both the Electoral Commission and the Metropolitan Police. The scandal, surfacing as Reform opened its annual conference, raises enduring questions about the price of political ambition and the fragil