When an influential centre-right Tory, who has served in Theresa May's cabinet, says that the Prime Minister's Brexit plan is the "worst of both worlds" and a "fudge I cannot support", it is clear beyond doubt that the PM's most important policy is in trouble.
For Justine Greening, the proposal to follow EU rules for the production and consumption of goods and food, and to collect tariffs for the EU, is neither properly leaving the EU or a rational "softer" Brexit.
What she says she fears, in an article for the Times, is Parliament rejecting May's plan, but finding it completely impossible to force through a more satisfactory relationship with the EU.
So - and this is something of a shock - she has come round to the idea that there should be a further referendum.
And importantly she thinks there should be three choices on the ballot paper, May's package, Brexit with "no deal" or remaining in the EU.
That would necessitate all of us being asked to pick our first and second preferences out of the three, and the result probably being decided on second preferences.
The theory is this would settle this nation-sundering question once and for all. Which could be a naive hope, but may be worth the risk for Tory MPs if the alternative is the collapse of their government.
Greening is convinced that her position will seem the only sensible one perhaps as early as close of play Monday, after the Brexiters of the European Research Group have attempted to frustrate May's Chequers compromise with their amendments to the Trade Bill.
So for many, Greening's promotion of a tripod plebiscite will be seductive. The former education secretary believes she already has support from disappointed Remainer Tory MPs, like herself, and disappointed Brexiter MPs.
Greening may have lit a fuse. There's only once certainty - Theresa May will be furiously trying to blow it out.