The empty threats of an irresponsible chancellor.
Second, the threat must be seen to have a chance of being carried out. Despite all the talk of Project Fear and the criticism of scaremongering, the threat or rather promise of refusing a currency union with an independent Scotland was a realistic prospect, as were most of the other warnings. While not a threat per se, the warnings of how an independent Scotland would be affected by a drop in the price of oil in fact underplayed how serious the drop in revenue would have been had Yes won.
George Osborne and Alistair Darling's threat of an emergency budget should the country vote to Leave next week therefore fails on all counts. First and most pertinently, George Osborne's not going to be in a position to present a budget in the first place. Even if David Cameron doesn't resign immediately as I imagined yesterday, he's likely to announce a fairly imminent departure. Osborne is almost certain to stand in the Tory leadership contest, so win or not, he most certainly won't be chancellor.
Next, as most commentators quickly pointed out, the tax rises and spending cuts Osborne and Darling set out (PDF) would almost certainly result in a recession whether or not the reaction to leaving is as dramatic as they predict. Darling's claim that he's more worried now than he was in 2008 is ahistorical nonsense. Darling and Brown have both previously commented that if they had not acted in the way they had as market turmoil and panic spread following the bankruptcy of Lehmann Brothers, the whole banking system was in danger of collapse. However serious the market reaction to a Leave vote would be, it would not result in the banks having to close and ATMs being left empty. The only responsible thing to do would be to wait and see what happens, and then if the economic fallout is damaging as claimed, the response would be to cut taxes and increase spending, as Darling of course did in 2008.
If then by some marvel of the universe Osborne was both still chancellor and decided to pursue his punishment budget, it would be voted down. The now 65 Tory MPs who have said they oppose it would win the day on their own, without the need of Labour, with Jeremy Corbyn and John McDonnell both saying they would oppose such a ramping up of austerity in any case. Corbyn even managed to get a laugh out of Cameron at PMQs by congratulating the Tory MPs supporting Leave on their sudden conversion to anti-austerity.
In the end though, it all comes back to the irresponsibility of Cameron and Osborne. Their refusal to confront their backbenchers in the way that say Blair did, instead giving in to their demands, has inexorably led to the very real risk the country will vote to make itself permanently poorer and more insular next week. Osborne's threat to make things even worse with an emergency budget isn't him cutting off his nose to spite his face; it's the equivalent of the dictator in the bunker ordering a non-existent army to commence blowing up bridges and destroying crops. Remain or leave, Cameron and Osborne must go. And soon.