lock step

from The Collaborative International Dictionary of English v.0.48

Lock step \Lock" step`\n.
   1. A mode of marching by a body of men going one after
      another as closely as possible, in which the leg of each
      moves at the same time with the corresponding leg of the
      person before him.
      [1913 Webster]

   2. Hence: (fig.) The slavish copying of one person's actions
      by another; as, party members who vote in lockstep with
      the leadership.
      [PJC]