Is Cameron slipping?

David Cameron's poll lead may be slipping.

There's an interesting parallel here with Obama. I was in the US just after his trip to Germany and a considerable poll lead. Then it started to slip. Analysts were convinced that he had failed to 'seal the deal' with the electorate who were intrigued by him, liked him but weren't convinced. Attack ads from McCain started to have an impact.

Is it the same for David Cameron?