It's becoming increasingly clear that the public voted for a form of Brexit that is unobtainable due to the Irish border. It has nothing to do with negotiation ability. We just can't leave without a backstop. Nor can we leave with no deal either, as it results in the same underlying problem.
Because of that, the only option on the table is a form of Brexit that, while satisfying some of the "mandate", ultimately has a good chance of putting us in a position of less control than we had before. We even have Brexit-supporting MPs saying that it's worse than staying in the EU, and in some respects, they are right.
The options available to May are dwindling fast. The only tools she has left is to try to push the deal through, and if it does fail (which is likely), then try again a second time.
If neither of those work, then the only realistic option I can see is to extend Article 50 and hold a referendum on the deal, either with or without the option to remain included. Either way, the only way no deal could possibly happen is if the public votes for it in a new referendum. But even then, I don't think the politicians would give the public the choice if there's a good chance of that happening. They can't take the risk.
In my view, we're either leaving with this deal, or we aren't leaving at all.