The important vote on Tuesday will be on the timetable, or programme motion, for the Withdrawal Agreement Bill, the law that must pass before Brexit.
The government wants it on the statute book by 31 October.
Labour will try to humiliate the PM by forcing a delay.
One minister tells me that the programme motion is therefore the “real meaningful vote”.
Tory rebels say they will probably back Boris Johnson's timetable if he enshrines the protection of environmental standards and workers’ rights in the bill and if the bill transfers to Parliament power to decide whether transition to full Brexit is to last 14 months, 26 months or 38 months.
But if Johnson gives in to the Tory rebels he risks alienating the Brexit Spartans of the ERG.
Tuesday does feel like make-or-break for Johnson’s Brexit (though obviously the history of Brexit has been littered with supposed crunch days that became nothing).