Most of this presidential election year will overlap with the Chinese Year of the Rat, which starts two days after Super Duper Tuesday on February 5. As far as the Republican nomination is concerned, many commentators have implied, this is wholly appropriate.

For who but a rodent would want to stand between the first female or first black President and the Oval Office?

Besides which, the opposing field consists of a cast who can be and have been dismissed on these pages as “five boring white men”. It is, therefore, a dismal yawn involving Old Rat (John McCain), City Rat (Rudy Giuliani), Country Rat (Mike Huckabee), Mormon Rat (Mitt Romney) and Dead Rat (Fred Thompson), paling into insignificance compared with the Democratic Party's struggle between Hillary Clinton and Barack Obama.

Such a dismissive attitude might be understandable, but it is profoundly mistaken for three reasons.

First, while a coronation is fine within a political party it should surely not occur in a battle between two of them. Americans deserve a meaningful choice. The notion that Mrs Clinton or Mr Obama should become President virtually by acclamation because of their gender or race, or as a simple repudiation of the Bush years, is surreal. The United States and the wider world will be best served by a serious struggle.

Secondly, far from being “all the same”, these supposedly boring white men represent an extraordinary collection of diverse opinions, most of which deviate from the established Republican norm. Mr McCain is a long-term maverick with stances on limiting the clout of money in US politics (fat chance), hitting the tobacco industry hard and climate change that defy the conservative stereotype. Mr Giuliani's positions on gays (pro), guns (anti) and God (cautious) deviate wildly from the typically Republican.

Mr Huckabee is, admittedly, a Baptist minister, though not of a censorious fire-and-brimstone form, and he is pretty tepid in his enthusiasm for free-market economics. Mr Romney's views on the issues seem to vary according to which state he is campaigning in at the time, but his faith alone renders him an unusual Republican contender.

For the esoteric, there is also Ron Paul, a libertarian purist, who has raised a fortune on the internet to back his quest to abolish income tax and close down all US bases overseas. The only really orthodox traditional Republican is Mr Thompson, and a lot of good that has done him so far in this election.

So, thirdly, it is almost certain that the eventual Republican standard bearer will be of a different hue from those who have been selected for the past 30 years. That alone has to be not dull but immensely interesting. In many ways, it is far more intriguing than what is happening among the Democrats. Mrs Clinton and Mr Obama have ideas and a political outlook very similar to the Democrats who have been offered to the American people for aeons.

Stick Al Gore in a skirt (not a comfortable thought), provide John Kerry with a Kenyan father (quite hard, I admit) and, hey-presto, this 2008 showdown is business as usual for the Democrats. If the two main rivals were called Harry Clinton and Brian Obama Smith it would be tediously familiar. Contrary to conventional wisdom, it is the Republicans who have the more stimulating competition.

Who will win it? If the pundits are to be believed, the Republicans are set for a war of attrition that will last for months more - perhaps even to their convention in September - while the Democrats will wrap up the prize one way or the other relatively shortly. This could be correct, but again I think precisely the opposite could be argued. Indeed, in the light of the South Carolina primary result - and despite the narrow margin of victory for John McCain - I will be reckless enough to assert that the so-called “endless” Republican fight is on the verge of being settled.

This is partly because of the bellwether factor. Some states establish themselves as almost spookily accurate predictors of wider sentiment. Come November, the state to watch is Missouri. It has, with the single exception of 1956, backed the winner in the electoral college ever since 1904. It would seem to be cheaper but no less accurate just to abolish voting in the other 49 states and let Missouri do it.

For the Republican caucus and primary season, South Carolina is the de facto Missouri. Since 1980 the man who has won here has always captured the nomination. This is not as strange as it sounds. South Carolina is a reliable Republican state come the election proper (unlike Iowa, New Hampshire or Michigan) and the demography of the people there who turn out to cast ballots in its primary is close to the party's electorate overall.

It is a fair bet that Florida will follow South Carolina's example when it votes next week and from there the road to effective victory on February 5 will suddenly become totally clear.

In that case, Mr McCain will be the Republican champion and a very credible one too. By coincidence, his birthdate, August 29, 1936, makes him a Rat in the Chinese calendar. They have a more charitable view of that creature in the East than we do. Rat people are said to be endowed with enormous leadership skills and are the most organised, meticulous, intelligent and cunning of the twelve animals that constitute Oriental astrology. Mrs Clinton and Mr Obama should regard him with fear. Not Old Rat, but, maybe, King Rat in the end.

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