The Democrats set out to achieve six things during the four days of their convention and succeeded handsomely on all six fronts: show unity and dispel the media-driven narrative of a party deeply fractured between Clinton and Obama; introduce the Obamas as a couple who share the concerns and values of ordinary folks; explain why change matters; explain it in bumper sticker or kitchen economics language; draw sharp contrasts with the Republicans and attack the McCain platform; and overcome lingering scepticism in the country about Obama's depth, gravitas and readiness to lead.

For the first task, the most important speakers were Hillary Clinton on the second day and Bill Clinton on the third. The Obama camp could not possibly have wished for more emphatic endorsements or better performances from the two in declaring their support for Obama: they promised to work enthusiastically for him and called on all their supporters to join in an all-out effort to elect him president. The message of party unity and harmony, and the risks to the party and its progressive agenda of divisions in a closely contested race, were also seamlessly woven by former presidential candidates Al Gore and John Kerry.

The introduction of the Obamas to ordinary Americans was begun by Michelle on the first night and completed with a video tribute to Barack Obama and then, of cours,e his own acceptance speech on the fourth night. They spoke in simple terms of their struggles as poor kids given extraordinary opportunities by the strength and sacrifices of their families, the resilience of parents or grandparents, and the social safety nets of the American system.

They emphasised the importance of their own children to their daily lives. They spoke of an upbringing characterised by hard work, a world of food stamps and scholarships, and a culture of community service above income maximising choices for individual fulfilment.

Barack Obama systematically rebuffed and methodically demolished every single line of attack against him to date. One of his most poignant stories was about his mother, while dying of cancer, arguing with the insurance company over payment for her treatment. Recalling other similar stories, he said he had no idea what sort of lives McCain thought celebrities led, but this had been his, Obama's, life.

Other key goals were met by a star-studded cast, starting with the surprising and deeply moving appearance of Ted Kennedy. It was gripping drama at its best as speaker after speaker explained why the past eight years have been wasted opportunities during which the Republicans have squandered the peace and prosperity inherited from the Clinton administration. The memorable lines included Hillary's ''No way, no how, no McCain''; Gore's confession that he believed in recycling, but not of the Bush Administration; Bill Clinton's bewilderment that the Republicans should expect to be rewarded for eight bad years with another four years; and Joe Biden's litanies of ''That's not change, that's more of the same''; and ''John McCain was wrong; Barack Obama was right.''

Biden, Kerry and Kennedy also took up the challenge of contrasting Obama's superior judgment on some of the biggest foreign policy and national security choices of recent years with McCain's instinctive preference for belligerent rhetoric over measured diplomacy, backed by might when required. Bill Clinton expressed it in the form of others being impressed more by the power of American example than by the example of American power.

Obama himself abandoned soaring lofty rhetoric for a politically far more effective speech wherein he castigated McCain for being tough on talk but weak on strategy, threatening to follow Osama bin Laden to hell while refusing to go after him in the cave in which he was hiding, and lacking in the temperament (interesting choice of word, that) and judgment to be president in the 21st century. Noting McCain's voting record of 90 per cent agreement with George W.Bush, he said he was not prepared to bet on a 10 per cent change candidate. McCain could not be said not to care; he just didn't know and didn't get it.

Obama spelt out what change would mean for the average American taxpayer, worker and consumer for job and social security, petrol and health costs, educational and social opportunities. In each case, he subtly reminded his audience of McCain's age. On the opening night, Kennedy had passed on the torch by rephrasing ''The dream never dies'', when his own presidential bid ended decades ago, into ''The dream lives on'' in Obama. On the closing night, Obama ended by invoking Martin Luther King's ''I have a dream speech'', whose 45th anniversary it was (serendipitously for the Democrats, given their nominee).

On the surprise choice of Alaska Governor Sarah Palin as his running mate, McCain's positives are outweighed by serious negatives. He managed to crowd out discussion of Obama's masterly acceptance speech from the nation's airwaves. He cemented his reputation as a maverick, prepared to take bold risks instead of playing safe. And he rallied his own base by picking a solidly conservative woman who is strongly pro-life, a lifelong member of the National Rifle Association, a supporter of conservative appointments to the Supreme Court, a Washington outsider to the point of being unknown, and a committed reformer.

McCain made a blatant play for disaffected Hillary Clinton supporters in choosing a woman. The move, revealing an astonishingly patronising and dismissive towards women that demeans them, is likely to backfire. The Clintonistas' anger at their own party persists because they believe she was the most qualified, experienced and competent candidate: her being a woman brought added excitement. To be asked to support a Republican ticket that contains a woman ultra-light in experience will enrage them and rally the Democratic base instead.

Palin just does not measure up on qualifications and experience. Several other prominent Republican women have superior intellectual, financial, executive and political capabilities. McCain had pulled even in the polls by relentlessly attacking Obama's thin re{aac}sume{aac} and questioning his readiness to be commander-in-chief. Just as this line of attack on Obama has traction, the 72-year old cancer survivor offers someone with even less experience and lower qualifications to step into his shoes from day one if necessary, should there be a medical emergency at 3am. CNN commentator Paul Begala has called McCain's choice of Palin ''shockingly irresponsible''.

The first executive decision the two candidates have made is their choice of running mates. Obama has chosen someone known, familiar, reassuring and with the requisite gravitas to step into his shoes if called upon to do so. McCain has demonstrated a flair for recklessness that will gamble the nation's future on his desperation to win the election. It should be a no-brainer. But then, as Winston Churchill famously said, the best argument against democracy is a five-minute conversation with an average voter.

Ramesh Thakur is distinguished fellow at the Centre for International Governance Innovation and Professor of Political Science at the University of Waterloo in Ontario, Canada.