It is 36 years since Chicago police went on the rampage against anti-war demonstrators in the streets outside the most electrifying Democratic convention of the past half century. Today, another war, another anti-war movement, another city, and another Democratic convention, this one beginning tonight in Boston. Much has been transformed in American life and American politics over the past 36 years. There will be little of the mayhem in Boston 2004 that marked Chicago 1968. One thing, though, is still exactly the same. As the police ripped into the demonstrators in Chicago, the stunned crowd chanted: "The whole world is watching." Today, in very different circumstances, the whole world will be watching again.

The world will not be watching out of any expectation of witnessing the kind of gritty political dramas which occasionally still marked nominating conventions in those earlier times. Like British party conferences, but on a far more extravagant scale, US conventions long ago became entirely presentational events aimed at television viewers back home rather than at party enthusiasts in the hall. Yet the whole world will be watching Boston this week none the less. It will be doing so because there has never been a US presidential election in which the interests and sympathies of the peoples of the world are more at stake than this one. George Bush has been the most divisive and dangerous president to occupy the Oval Office. It is not just a narrow majority of American voters who, according to current polls, want Mr Bush to be defeated in November. It is an overwhelming majority of the citizens of other lands, those of this country very much included.

Senator John Kerry comes back to his political base in Boston as overwhelmingly his party's preferred choice to topple the incumbent president. But he also arrives leading by a nose in the match-up with Mr Bush. Since he added Senator John Edwards to his ticket as vice-presidential running-mate, Mr Kerry has led in over a dozen reputable nationwide polls. Mr Kerry may not have excited the media or the Michael Moore militants very much these past few months. But do not be misled. This is not a volatile campaign and Mr Kerry is steadily building a strong position in the polls, especially in crucial swing states - places like Florida, Ohio, Missouri and New Hampshire - that will again decide the outcome, while also harboring his big campaign war chest for when the going gets tougher. The longer the campaign has gone on - this contest effectively lasts for nine months - the better shape Mr Kerry seems to be in, and the shrewder his decision to play the long game.

Nevertheless, the hard pounding of the 2004 campaign is about to begin, and it will get much harder and much dirtier once the summer is done. Mr Kerry still has heavy lifting to do before he takes his support across the gap between the 47% or so of the electorate who seem determined to vote for him anyway and the around 53% of voters who say it is time for a change - and who are thus making themselves available to support him if he can complete the sale. The Boston convention - which Mr Kerry addresses on Thursday in his acceptance speech - represents the key opportunity for the Democratic challenger to move his campaign across this gap. It is a chance to present a program, a man and, above all, a better way of governing America. In the end, US voters have got to want Mr Kerry in as well as wanting Mr Bush out. That is why the senator's task this week is to move from being Mr Not-Bush to being a positive candidate in his own right. The question posed at Boston is: "Why Mr Kerry?" Here is the senator's moment to answer, not only for Americans, but also for a world that is watching and willing him to rise to the occasion.

© Guardian Newspapers Limited 2004

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