Tailism is a tendency in politics that decides to chase public opinion, or institutional opinion, instead of having a program. Identity politics is a form of tailism.
The American left is tailist. The CPUSA moved towards social democracy in the 80s and led the emboldened socdems in the party, Angela Davis and the Committees of Correspondence, cause a split. Tailing the people trying to change the nature of the party only meant that now, in the Sam Webb and Joe Sims era, the CPUSA has no meaningful difference from the DNC.