So, where are we? There is now an open effort to get the 48 letters required to force a vote of no confidence in Theresa May. Personally, I don’t think it is a racing certainty that this succeeds. The ERG WhatsApp group has had some influential people urging caution, and telling people not to put their letters in.
But if the letters do go in, the risk is greater to Mrs May than conventional wisdom has it. In the privacy of the ballot box, I think a decent chunk of the payroll would vote against the Prime Minister. Interestingly, one minister who is agnostic on the deal told me that they thought May was now an obstacle to it passing; that a new leader would have a better chance of getting it through.
Even the possibility of winning a no confidence vote could be dangerous for her. There are a decent number of MPs who want her to continue as PM until she passes the deal, then hand the baton to a new leader who can handle the trade negotiations and secure terms that are more palatable to Brexiteers. But the rules around a no confidence vote mean that if she wins it she couldn’t be challenged again for a year. If there is a risk of that happening and her staying on for that long, that will tip some more MPs into voting against her, making this a tighter vote than one might expect.