FOR a speech with such profound consequences for domestic British politics, David Cameron's European address arguably found its most important audience abroad.
The calculus that underpins the prime minister's strategy is this: the more concessions he wins from the rest of the EU when renegotiating Britain's membership, the more British voters will join him in 2017 in voting for that membership to continue.
That was why the speech was intended to be made outside Britain, as geographic proof that Mr Cameron is serious when he says his true intent is not to leave Europe but to reform it. His point: to get the deal he has promised to promote, Mr Cameron needs other EU leaders' help.
So the speed of the French response to his speech was striking: minutes after he spoke, Laurent Fabius, the French foreign minister, was criticising a "dangerous" policy and insisting Mr Cameron's challenge to "ever closer union" must fail.
He can expect more of the same in Brussels next month during talks about the EU's budget for 2014-20. He wants to cut European spending, but why, his opponents will ask, should anyone listen to a man whose country may not even be at the table?
The French response was discounted in London. One European response mattered: Angela Merkel's. Germany's chancellor is Europe's dominant leader. Her willingness to accommodate Britain's desire for a rebalanced relationship is critical. Mr Cameron has staked a lot on his belief that she will back him to keep Britain in the EU.
Her reaction has raised cautious Conservative hopes that his gamble will pay off. Yes, she cautiously noted that the EU only ever proceeds by compromise, and warned Mr Cameron that he is not the only leader with "wishes". But she did not dismiss him. She promised to talk.
Mr Cameron would prefer that discussion to produce a whole new EU treaty, a document codifying his pro-market reforms. But many other leaders, including Mrs Merkel, are wary of yet another treaty.
Hence Mr Cameron says Britain is ready to proceed without one: anything to keep Mrs Merkel engaged.
Only by talking can Mr Cameron hope to win back British control on employment rules, market regulation, farming and maybe even a few aspects of immigration policy. In exchange, Mrs Merkel will expect British backing for German ideas on financial regulation and economic coordination within the eurozone.
Mr Cameron's big speech has started a big conversation with Mrs Merkel. It will likely decide both his political fate and Britain's place in Europe. (© The Daily Telegraph, London)