Leading article: Time for the Democrats to rally around Mr Obama

The epic contest for the Democratic presidential nomination looks as though it is at last winding down. With his convincing victory in North Carolina and the narrowest of defeats of Indiana, Barack Obama finally appears unbeatable. Mrs Clinton, whose fighting spirit has been one of her greatest assets through this protracted campaign, would be wise to call it a day.

We say this with some regret. It has been a thrilling ride and, for those of us watching from abroad, a veritable primer in US politics and geography. Mrs Clinton has gone from being the nominee to beat, with a war-chest as inexhaustible as her contacts book, to defiant underdog, and ultimately to doughty pugilist on an equal footing with her younger rival.

Battle-hardened and resilient, she campaigned best when the pressure was greatest. If her run is reaching its end, she cannot be accused of faintheartedness, or lacking capability for the job. As the first truly plausible female candidate to run a presidential campaign, Mrs Clinton has shown that, for the right candidate, what is indisputably the world's top job is within reach.

Probably, she was not the right candidate. Too much political baggage came with her brilliant, but flawed, husband. And two Clintons after two Bushes may have had too much of the dynasty about it for voters' comfort. However competent she appeared, there were also unanswered questions about exactly who she was and what she stood for. After eight disastrous years of George Bush, Americans seem in no mood for that sort of gamble.

Mrs Clinton's defeat, of course, is Barack Obama's victory. His rise, from a standing start as a young, relatively untried, black Senator, has been at once remarkable and inspiring. Hard work, unbounded energy, a rhetorical gift and a sense that there was everything to gain and nothing to lose doubtless contributed to his success. But it was the total package of thorough-going change that clearly appealed to American Democrats.

The post-Bush mood is clearly for a fresh start, and no one personifies a new America more than he does. The party rank and file have shown they will take the risk of nominating a young black senator for President. It is this sense of adventure, this willingness to give promise a go, that is one of America's most enviable traits.

Much has been made of the damage so long and divisive a contest has inflicted on the Democrats' presidential prospects. Assuming he is nominated, Mr Obama will need to spend much time courting opponents within the party. Mrs Clinton will need to put the party's interest above her own ambition. We doubt that she would, or should, accept an invitation to be his running-mate, even if it were extended. But his choice will say much about the sort of president he wants to be.

For all the drawbacks of this long and bitter campaign, however, it may not have been entirely negative. It has tested both candidates, but especially the younger man, in a way that was absolutely necessary. Barack Obama has matured as a candidate before our eyes. He has demonstrated that he can cope with reverses; he can adjust his register; he can present his case. He has shown, too, that he has thought through one of his country's most deep-rooted and enduring problems – summed up in the single word, race.

It is time for the Democrats to bury their differences and prepare to do battle with John McCain, the Republican who will be their opponent in November. With youth pitted against age, and promise against experience, we look forward to another absorbing contest. And, whatever the outcome, Mr Obama will be an infinitely better candidate for the trials he has endured along the way.

For rolling comment on the US election visit: independent.co.uk/campaign08