 Complete the following phrase:  The Groups leaders continued to protest what they saw as a gradual abolition of intra-Party democracy throughout the early 1920s and joined Leon Trotskys Left Opposition in 1923. In 1926 Sapronov and Smirnov formed the Group of 15, which joined the United Opposition headed by Trotsky, Grigory Zinoviev and Lev Kamenev. They were expelled from the Communist Party at the 