After the October Coup, Grigoriev participated in the dispersal of the leadership of the Zemstvo Union headed by Prince Trubetskoy. In December 1917, Grigoriev became a member of the reformed Main Committee of the Zemstvo Union, in which he worked as a statistician until its liquidation in late 1918. Since December 1918, Grigoriev was a member of the RCP (b), becoming one of the first Soviet artists to be a communist, having already 20 years of party experience by 1938.