Thatcher called it “rachet socialism”. they never stop and whenever they have power, they give the rachet a couple of pulls. when they are out of power, their opponents (i.e. the stupid party) NEVER turns the rachet any pulls backwards, so it becomes inevitable that the left will eventually get everything they want. ugh.
One of my seminary professors called it “thesis, antithesis, and synthesis.” Same principle - socialism (or sin) keeps creeping forward.