Answer
York South was the riding where Arthur Meighen unsuccessfully contested a by-election. Meighen, a former Prime Minister, sought to regain a seat in Parliament after losing the 1926 general election. However, he faced a strong challenge from Liberal candidate William Mulock, who had the support of the sitting Prime Minister, William Lyon Mackenzie King. Despite Meighen's efforts, Mulock ultimately prevailed in the by-election, preventing Meighen from returning to Parliament.