The politics of HS2 are difficult for Boris Johnson, especially since so many Tory MPs hate the £100bn plus cost, the destruction of ancient pasture and woodland, the perceived harm to their rural constituents.
But the bigger politics for Boris "another-blue-brick-in-the-red-wall" Johnson is the perception of whether today's modified version is seen as an upgrading or downgrading of the portion north of Birmingham.
His colleagues insist what is planned will be central to his promises to transform both the infrastructure and the prospects of the North.
As I understand it, this is about making sure the high-speed line is part of a new network of railway lines "connecting all the northern cities" (in the words of a government source).
So HS2 to Birmingham will be given the green light.
HS2a from West Midlands to Crewe will also be approved.
And HS2b will be reworked as part of a bolder regeneration scheme, a sort of "much more jam tomorrow" for parts of England north of Birmingham.
It will all sound ambitious. But given that shovels-in-the-ground work on these Northern Powerhouse projects are years away, quite a lot of trust will be needed that yet another southern PM won't ultimately betray the North (again).
PS. You may remember that the Northern Powerhouse is the child of the former chancellor George Osborne. But he can expect little gratitude or reward from Boris Johnson.
And I am told he will have no enhanced role in these ambitious new plans.
The point is that Dominic Cummings, the PM's chief aide, blames Osborne - among others - for the massive HS2 cost over-runs, which have seen its estimated cost treble to more than £100bn.
Here is what a "number 10 source" says about him: "Osborne is one of those most guilty of blowing tens of billions on HS2 and it would be criminal to let him anywhere near any major project ever again".