 Complete the following phrase:  With Trotsky finally on the sidelines, the Zinoviev-Kamenev-Stalin triumvirate began to crumble early in 1925. The two sides spent most of the year lining up support behind the scenes. Stalin struck an alliance with a Communist Party theoretician and Pravda editor Nikolai Bukharin and Soviet prime minister Alexei Rykov. Zinoviev and Kamenev allied with Lenins widow, Nadezhda Krupskaya, and Grigory Sokolnikov, the Soviet Commissar of Fice and a non-voting Politburo member. The struggle became open at the September 1925 meeting of the Central Committee and came to a head at the 