Well the backstop was what most Tories claimed that they were opposed to. If it was restricted to NI only and the DUP were on board with that then their concerns would seem to have been allayed. Throw into that a number of Labour MPs who want a deal and might be persuaded by a committment to a level playing field and you have yourself a majority.
The problem of course is that there are many in the ERG who seemingly only want no deal now. How many of them there are remains to be seen.
Also, it is unlikely that Ireland are will to accept much watering down of the NI backstop element, they're going to want cast iron guarantees that this can't break down in a couple of years time.
There is a path there to a deal but it's terribly narrow and time is very much against us.