With the publication of his long-awaited education bill, Charles Clarke has finally drawn the battle lines in what is set to be the prime minister's greatest parliamentary test since the Iraq war.
The education secretary has been as good as his, and Tony Blair's, word and refused to give any ground on the principle of allowing universities to charge variable fees.
Clarke made significant concessions
But, as predicted, he has offered concessions aimed at placating rebels concerned about the effect the package will have on students from less well-off backgrounds.
The package, which adds up to as much as £3,000 a year available to nearly a third of students, has delighted some of the rebels because it effectively writes off the fees.
But it has done nothing to answer concerns of the most hard-line opponents.
So that leaves two major questions hanging over his statement.
Has he done enough to whittle down the threatened rebellion and spare the prime minister a potentially fatal defeat?
And have the concessions been so great as to, in effect, turn the proposals into "a complete mess", as suggested by Tory spokesman Tim Yeo.
On the line
On the first, there have been signs for some time that of the almost 160 MPs who have signed a Commons motion opposing the policy, a good number have been reassured.
Leading rebels like Dr Ian Gibson believe there are still around 100 who might vote against the bill later this month. And that would still be enough to defeat the government.
Blair's leadership is on the line
And if that happened, it is hard to see how Mr Blair could then avoid considering his position as prime minister.
After all it was he, not the rebels - at least not in public - who claimed his leadership would be on the line over this.
The issue of variable fees is still the big sticking point and there are plenty of rebels who will simply never be won over so long as that remains part of the proposals.
Speaking after the statement, senior rebel Nick Brown suggested he was still unhappy with the package.
As far as he was concerned the policy was still producing a market in education.
He also expressed the concern of many backbenchers that it was only a matter of time before the £3,000 cap on fees was lifted.
On backbencher said: "University chancellors are already squealing that the government's concessions undermine the bill by giving with one hand and taking away with the other.
Fees policy has sparked a major backlash
"They will be demanding more money as soon as they possibly can."
That second concern could signal trouble further down the line if there are moves to lift the cap, despite the fact that Mr Clarke said such a move would require agreement by both Houses of Parliament.
Others, however, had simply been looking for changes to the proposal which would help less well off pupils. And it is that group the education secretary has targeted.
But even some of those who welcomed the concessions remained opposed to variable fees.
It will still be an edge-of-the-seat vote in the Commons, but the prime minister appears confident he will not have his leadership threat tested to destruction.
Of course, this all comes against the background of the prime minister's other troubles, most notably the Hutton inquiry.
He may be playing on backbench fears that, if they do inflict a defeat on him at this time of weakness, they may actually force him from office.
And the majority are - at the moment at least - still far from eager to press that nuclear button.