Georges Clemenceau was a journalist, politicial writer and politician of immense importance, later President of France (1917-20).
Clemenceau knew Whistler in Paris in the 1890s when he wrote for La Justice and L'Aurore. Clemenceau was known as an admirer of Impressionist painters, especially Monet. He was Minister of the Interior at the time that Whistler and his friends were negotiating the sale of Arrangement in Grey and Black: Portrait of the Painter's Mother y101 to the French Government, and strongly supported the proposal to buy it in 1891-1892.
Encyclopedia Britannica, online edition; 'Georges Clemenceau', Larousse online; 'Georges Clemenceau', Wikipedia.