The most important thing about the first US presidential debate was that John Kerry won it. A hardening conviction among the political classes that George W. Bush was coasting to a second term was broken. Against predictions, Mr Kerry came across as focused and composed, Mr Bush as distracted and truculent. Those who had rushed to write off the Democratic contender as another Michael Dukakis are now scrambling for explanations as to why they might have been wrong.

I say might because the outcome on November 2 is still uncertain. The latest post-debate polls point to a dead heat but we have seen how quickly public opinion can move. The two men meet again this evening in St Louis, Missouri. There will be a third encounter beyond that. Yet in important respects the way in which the campaign is framed has shifted to Mr Kerry's advantage.