The Lib Dems claim that 80 MPs will vote against Article 50, at least without the guarantee of a second referendum.
But that depends very heavily on the SNP, by no means all of whom should be regarded as onside.
Mhairi Black said today that she had "held her nose" just to vote Remain in the referendum.
She will not have been the only one, and there may very well have been Leave voters.
Assume, however, that all 54 SNP MPs, plus the two more whom the party has had to suspend, were indeed to vote with the eight Lib Dems.
That would give a total of 64.
The three members of the SDLP are also said to be of that mind. Presumably, so are the three members of Plaid Cymru.
If the grand total is 80, then all of 10 other MPs intend to rebel against either the Conservative or the Labour line.
Keep in mind that this was Owen Smith's flagship policy.