Who is Nikolai Ivanovich Bukharin from The Gulag Archipelago, 1918-1956 and what is their importance?

A prominent Communist Party official and economic theorist, Bukharin becomes a member of the Politburo in 1924 and General Secretary of Comintern after 1926. As his beautifully phrased but empty Constitution for the USSR is being adopted, he falls from Stalin's grace—although Stalin plays cat-and-mouse with him for months. Early in 1937, Bukharin begins a hunger strike to get a hearing and clear his name. Stalin treats it as absurd that they would expel him. When Bukharin writes a final "Letter to the Future Central Committee" pledging loyalty to everything that has been done to date, Stalin deems him ready for trial. Identifying intention and action proves him a traitor and he is shot.