Each Republican candidate believes he is best served by staying in the race – that if he can end up being the last man standing against Mr Trump, that he can win. But the truth is that none of them can win without co-operating. But who should sacrifice himself for the good of the cause? The other guy!

There has been a lot of talk about a possible brokered convention – a laughable assertion since there are no more “brokers” left in the Republican Party. But actually, what we really need isn’t a brokered convention, it’s a brokered primary. If there were ever a time for a party boss in a smoke-filled back room, this would be it.

The non-Trump candidates should find a way to hash out their differences and cut a deal today. Maybe that involves Mr Rubio agreeing to be Mr Cruz’s running mate – or vice, versa. Or maybe whoever has the most delegates after South Carolina stays in the race. But something has to be done.

Even if this were possible (it’s not), Mr Trump would portray this as a corrupt bargain. And he would have a point – the tactic would probably further harden his support.