In the wake of Lenin's death, various protagonists emerged in the struggle to become his successor: alongside Stalin was Trotsky, Zinoviev, Kamenev, Bukharin, Alexei Rykov, and Mikhail Tomsky. Stalin saw Trotsky — whom he personally despised — as the main obstacle to his dominance within the party. While Lenin had been ill Stalin had forged an anti-Trotsky alliance with Kamenev and Zinoviev. Although Zinoviev was concerned about Stalin's growing authority, he rallied behind him at the 13th Congress as a counterweight to Trotsky, who now led a party faction known as the Left Opposition. The Left Opposition believed the NEP conceded too much to capitalism; Stalin was called a "rightist" for his support of the policy. Stalin built up a retinue of his supporters in the Central Committee, while the Left Opposition were gradually removed from their positions of influence. He was supported in this by Bukharin, who, like Stalin, believed that the Left Opposition's proposals would plunge the Soviet Union into instability.