American Presidential elections have been compared with reality TV series or game shows, in which a gaggle of jumped-up nonentities aspiring to be celebrities are ritually humiliated in public and offered entertaining opportunities to self-destruct, until only one survivor remains. But this time round, a much more elevated analogy is sadly apposite.

The 2008 US election has all the makings of a Greek tragedy, in which noble heroes and heroines are forced to follow a course to catastrophe, divinely preordained as punishment for sins and blunders committed by their forefathers in the dim and distant past. In acting out their ineluctable doom, the eloquent protagonists do not just destroy themselves but also their cities, their nations and even their entire civilisations.

If this description sounds too grandiose, consider yesterday's results from the Pennsylvania primary. The outcome seemed to be precisely calibrated by the gods to maximise the agony of the Democrats. It gave Hillary Clinton just the support she needed to stay firmly in contention, but not quite enough to turn the tide in her favour.

Worse still, this result underlined the fear that senior Democrats have long been aware of, but have never dared to express in public: America may not yet be ready to elect a black President. Worst of all, it has created conditions for the possible election victory of a militarily belligerent and economically unqualified Republican candidate who supports many of President Bush's worst policies. Given the Bush Administration's domestic and foreign failures, the disasters in Iraq and Afghanistan and, most recently, the slump in the economy, the possibility of a Republican victory in November would seem to overturn every principle of proper democracy - and also the hope of America and its system of government being rehabilitated in the eyes of the world after the Bush years. The fact that Mr Obama and Mrs Clinton are both such impressive candidates, intelligent, sincere, articulate and in command of the issues, while John McCain does not qualify on any of these criteria only makes matters worse.

That Mrs Clinton will now carry on with her campaign is not just probable but essential. For the voting in Pennsylvania confirms that she has a much better chance than Mr Obama of winning the White House for the Democrats. According to the Associated Press exit polls published yesterday, 16 per cent of white Democratic voters considered race an important factor in the Presidential election and 43 per cent of these said they would either vote Republican or not vote at all, if Mr Obama were the Democratic nominee.

Given that Mrs Clinton's clear victory over Mr Obama in Pennsylvania followed similar results in other “must-win” states with large working-class constituencies, such as Ohio, Florida, New Jersey, Michigan and even New York and California, the conclusion would be fairly obvious, were it not for the political correctness that makes it almost impossible for American politicians or commentators to express such a view: Mr Obama may by unable to carry large industrial states with socially conservative white working-class populations simply because of his race. This is especially true now that the televised rantings of Rev Jeremiah Wright and Mr Obama's own gaffe about the “bitter” white working-class culture of “guns and God”, have reminded Americans that race is not just a matter of skin colour. Rev Wright embarrassingly revealed in his “God damn America” and “Chickens come home to roost” sermons that his African-American vision of America is be profoundly at odds with the white majority view.

The latest polls in the two most important swing states show Mr McCain easily beating Mr Obama in both Florida and Ohio, while Mrs Clinton comfortably beats the Republican in Ohio and is neck and neck in Florida.

Mr Obama has, of course, apologised for his condescension towards working-class church-goers and hunters - probably the most important group of floating voters in the electorally critical mid-Western states. He has tried even harder to dissociate himself from Rev Wright's anti-American tirades, which really have to be seen (on YouTube) to be believed. And Mr Obama's supporters have chastised Mrs Clinton for turning to “negative campaigning” and “scorched-earth” strategies in her desperation to stay in contention.

The trouble is that Mr Obama's efforts to suppress the race issue are doomed to failure. For the influence of Rev Wright on him is a matter of public record. Indeed, the phrase “Audacity of Hope”, which is the title of Mr Obama's political autobiography as well as his presidential leitmotif, is attributed in that book to a sermon by “my pastor, Rev Jeremiah Wright”. The Republican political machine, which demonstrated its mastery of the arts of character assassination in the two Bush presidential contests, will have no compunction in exploiting the Wright relationship and portraying Mr Obama as an anti-American in the general election, even if the Clinton campaign and the media observe a self-denying ordinance on the race and patriotism issues, as they broadly have so far.

The certainty of a no-holds-barred attacks by the Republicans brings us to the potentially most tragic aspect of this election. If ever there was an election the Democrats ought to win this is the one. Yet on the basis of the primary results so far, they are all too likely to lose it. Mr Obama may be marginally ahead of Mrs Clinton in the popular vote but the Democrats seem to have forgotten that all the votes cast so far have been by their own supporters. In the general election their candidate will have to win over Republicans and right-leaning floating voters. Most of the evidence so far suggests that the Repulicans will find it much easier to frighten voters about the prospect of a President Obama than a President Clinton.

Professional Democratic politicians now have the casting vote in their party's nomination and could yet force the two candidates into a “dream ticket” led by Mrs Clinton with Mr Obama as Vice President which would sweep all before it and would probably make Mr Obama unbeatable as a presidential candidate in 2012 or 2016. Yet the Democratic superdelegates who could now secure years of hegemony for their party seem to consider it “unfair” to use their professional judgment to overturn the “democratic” verdict of primary voters.

The Republicans will have no such compunctions about the fairness of launching personal attacks against a potentially vulnerable Democratic candidate. In this respect this Presidential contest may again manifest the tragedy of left-wing politics through the ages. Parties which care more about fairness than about power, end up achieving neither.

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