First it was Iraq. Then the language of New Labour.
Now contenders for Leader of the Opposition have disagreed over the merits of joint use of playground equipment in the name of a publicty stunt.
Andy Burnham, one-time health secretary, used a speech in the Commons to distance himself from the blunder when in government with Schools Secretary Ed Balls.
Burnham said in the Commons: "I rarely missed an opportunity to promote joint working between our two departments, although we can probably both admit now that jumping on a rope swing was, in retrospect, a promotional step too far."
At which point Balls, practising the new politics of positivity, said: "I enjoyed it."
But Mr Burnham abandoned the cost consensus to insist: "I beg to differ."
This contest is getting ugly.