Harris is off to a dream start-but it's too early to count out Trump Jonathan Freedland

Everything is going right for her and wrong for him. Kamala Harris has the encouraging poll numbers and the momentum. Donald Trump has the serial errors, the maudlin introspection and wobbling campaign team.

- Jonathan Freedland

In little over a month, the Democrats have pulled off one of the most extraordinary turnarounds in US political history, replacing a candidate who was shuffling towards nearcertain defeat with one soaring towards possible victory. Yet contained within is a lurking danger.

The sources of joy are not mysterious. Democrats this week headed to Chicago for a convention that felt like a party but everyone had imagined would be a wake. Before 21 July, they were tied to Joe Biden, a man who was on course to lose, and lose badly, in November.

The campaign has switched over - equivalent to rebuilding a plane in mid-air, say seasoned election hands and the candidate has taken to the task with ease. Twenty years younger and a lot more vigorous than her opponent, she has turned what had been Trump's most potent weapon against Biden - age - against Trump himself. He is now the candidate of the past, she the face of the future. Never mind that Harris is a senior member of the present administration, she has shaken off the burden of incumbency - a negative in most democracies - and cast herself as the turn-the-page option, aided by a powerful slogan: "We're not going back."