The immigration Rubicon is in front of us. The question is whether the prime minister is ready to cross it. On the other side lies controlling EU migration by quotas. What's left is the option of controlling migration by ending in work and out of work benefits. If the prime minister chooses quotas he will have crossed an irreversible line.
When Hugh Gaitskell was applauded for opposing Britain's application to join the then EEC at the 1961 Labour Party conference, his wife whispered 'all the wrong people are clapping'. Such will be the fate for Cameron because the modernisation of his party, on which he was elected leader, will be over. Control over European and immigration policy will have been ceded to the right.
But he won't do that.
Cameron is highly likely to pull down the kite that he persuaded Sir John Major to fly in Berlin two weeks ago and restrict himself to controlling migration through benefits, not quotas. But, to give him political space, his tone will be pure Daily Mail. He will shout loudly and carry a small stick. He will satisfy few in his party and few outside it because his room for manoeuvre is agonisingly tight.
Farage has sat on the quotas territory for years. Last week Labour's Yvette Cooper occupied the welfare tourism territory with her policy restricting out of work benefits to EU migrants. All that is left is an in-work benefits clampdown to stop Poles sending child benefit back to Warsaw, by no means the game-changer promised last month. Unless there's more, Cameron is left selling a Labour policy with Ukip language. Lipstick on a pig, as Sarah Palin used to say.
What can he do? Firstly, he needs a bigger story to sell. He needs a win over Ukip on its values, a win in Britain on benefits and a win in Europe with supportive allies who share the problem. Policy tweaks dissolve in a debate where mistrusted politicians utter disbelieved facts to an anxious public.
First, David Cameron should heed the YouGov poll for the Times, and attack Ukip values not reflect them. Matthew Parris was right in urging Cameron to abandon hugging Nigel close and recapture the moral high ground on which, after all, he started his leadership.
Second, the public think the immigration/benefits system is too lax. It can, within the rules of the Treaty be tightened up. Parties have already embarked on an arms race to see how far free movement can be pushed back. So, according to British Future's "How to talk about immigration" the PM should:
Announce reform of the UK border control, registration and benefits system- and what the limits of achievable reform are;
Set out the strategy to secure allies if he seeks to achieve fundamental changes to EU free movement rules as a 'red line';
Challenge the opponent of free movement on whether leaving the European Union is a price worth paying for border control repatriation;
Thirdly, it pays for the UK to be seen as positive European game-changer. Germany, France, Holland, Sweden, Denmark and Austria all face the same problems. A coordinated approach to benefits and cross-border cooperation is required to face the migratory flows from inside and outside Europe.
However, if the prime minister chooses the opposite and apes Ukip values, Labour policies and Daily Mail rhetoric, the only winner will be Nigel.