Sketch: Aspiration for all, whether you're white or black, Eton or Harrow

In one sense, David Cameron couldn't go wrong. After a tense week, the mayor finally gave Cameron the unqualified loyal support he needed. The Tories were "lucky" to have a leader with "integrity" tackling "big challenges", he said, one who would ensure that "clear skies" would quickly return.

This wasn't actually Boris, which would have been too much to expect. It was the Republicans' Michael Bloomberg, in a warm-up speech which name-checked the Prime Minister with awe-inspiring frequency, lavishing praise on him that his London counterpart would have choked on. Way to go, Dave! If you can't get your own, home-grown Conservative mayor to do the business, fly one in from New York to show him how it's done.

And certainly Bloomberg set the stage for a reasonably combative performance. Cameron tackled head-on the jibes about his poshnesss; even though he couldn't quite bring himself to use the E-word. "I went to a great school and I want every child to have an education. I want every child to have a great education. I'm not here to defend privilege I am here to spread it."

Never mind that this raises the grim prospect of schoolchildren across the country being compelled to play the Eton's trademark game, a terrifyingly pointless means of getting up close and personal with other boys while trying to scrape their skin off with a brick wall (one at which Boris, unsurprisingly, is said to have excelled). Or that the conceptual problem with spreading privilege is that once spread, it ceases to be privilege. Privilege Spread! It sounds like something Fortnum and Mason might patent.

It nevertheless did the job, in so far as any political speech can, in countering Ed Miliband's cross -dressing as "one nation" Disraeli, with an his own affirmation that the Conservative party is for everyone "North or South, black or white, straight or gay."

Part of the argument was that Britain was faced with a life or death choice between being a country "on the rise" like Brazil, Indonesia and China, or one "on the slide", such as "sclerotic over-regulated" economies like, well, Greece. As a means of dressing up the message that the Government was determined to preside over a longer period of austerity and deeper welfare cuts than anyone had feared, it was probably as good as any.

But his new, alternative catchphrase, "aspiration nation" sounds a bit clunky. Maybe the answer is to incorporate it into an election campaign song, set the to the tune of the old Martha and the Vandellas hit "There'll be dancin', they're dancin' in the street/ There's an aspiration, across the nation."

In dark times, worth a try at least.