The high-stakes game of parliamentary ping pong over the EU Withdrawal Bill continues. Last night, peers voted to insert a new meaningful vote amendment by Dominic Grieve into the text of the legislation. This sets up a Groundhog Day scenario for the Prime Minister, who now faces the fight with pro-EU rebels that she clumsily deferred last week.

When the Commons last voted on the question of the meaningful vote, it was clear the mutineers had the numbers to win. Though they were bought off with the promise of a compromise and backed down, the peace didn’t hold.

To the chagrin of Grieve, the government offered only a vote on an unamendable motion that MPs have “considered” the final deal with Brussels, not the right to direct negotiations in the event of the Commons rejecting it, or no deal being agreed. The promise of an essentially meaningless vote was unacceptable to the former attorney general, hence the move by peers to amend the bill again.

MPs will vote on the amendment tomorrow. But could the legislation end up passing largely unscathed? A fortnight ago, when it looked like the government would lose not only on the meaningful vote but also on a customs union and maybe even the European Economic Area, that would have been a bold suggestion. Now, however, it’s a much safer one to make.

Accounting for the nine or so Labour MPs who will likely either vote with the government or abstain tomorrow, Grieve will need around 14 Conservative MPs to defy the whip if his amendment is to pass.

Here is where it gets tricky: beyond himself, Anna Soubry, Ken Clarke, Sarah Wollaston and a couple of others, such as the recently resigned Philip Lee, Grieve cannot count on anywhere near that many of his colleagues as a matter of course. Nor can the bill be amended by the usual suspects alone. The best illustration of this is the Daily Telegraph front page which coined the “mutineers” descriptor for Tory rebels last November. Most of the MPs pictured did not then have a reputation as rebels or dyed-in-the-wool Europhiles but had been convinced that aspects of the bill needed improving for the sake of the national interest.

The problem for Grieve now is selling the meaningful vote as one such necessary improvement. I understand it is proving difficult. “They won’t have the numbers,” one of those MPs pictured on the Telegraph front page told me yesterday. “Most of us think the government’s amendment is fine. Dominic is a great legal mind, but politically, he's got this all wrong.”

The pool of potential rebels is getting smaller. Grieve’s claim that the rebels could collapse the government has alienated some of the waverers, as has his unwillingness to accept what many consider to be a reasonable compromise. Don't forget that the one thing that unites rebels past, present and potential is that all are broadly supportive of Theresa May and do not want to destabilise her. Tom Tugendhat’s argument that any vote on the final deal will be meaningful – as no government could survive a defeat – is a popular one that has convinced a number of those on whose support the mutineers might have counted.

Saving May used to mean saving her from Jacob Rees-Mogg and the ERG. It now increasingly means saving her from Grieve. (One rebel also suggests that the protracted row over the meaningful vote is dampening the chances of rebellion on the Trade and Customs bills next month.)

Plus, if the past months have taught us anything, it’s that most Tory MPs always err on the side of not defeating the government. And equally, for Labour Brexiteers or those representing constituencies that voted heavily to leave the EU, that Grieve's amendment is increasingly being spun as a wrecking one makes it harder to back. Tomorrow’s vote is shaping up to be another anti-climax.