Visitors to California could be forgiven for failing to realise that they have arrived at the latest hub of America’s political Universe.

There are few, if any, of the yard signs which proliferated outside homes in the early voting states of Iowa, New Hampshire and South Carolina. Television viewers are not bombarded every 15 minutes with another paid-for message approved by the likes of Hillary Clinton, Barack Obama, Mitt Romney and John McCain. And it is possible to sit down for a coffee without having to shake the hand of someone hoping to be the next leader of the free world.

California, with 36 million people and the eighth largest economy in the world, is big enough to absorb the most intense presidential election for a generation. It has 53 congressional districts, more than any other state, in 156,000 square miles that take in the ghettoes and star dust of Los Angeles, the beaches of the Pacific coast, rugged deserts and Silicon Valley.

The scale of this racially, economically and culturally diverse state ensures candidates cannot practise the close-up retail politics of Iowa and New Hampshire – while wholesale operations such as blanketing California with TV advertising are prohibitively expensive. In recent years none of this has mattered much because the Golden State’s presidential primary took place after earlier votes had already largely determined the nominees. But this time California has moved the election date forward to February 5, making it the biggest prize in the wave of 22 being awarded on Super Tuesday next week.

Whereas previously candidates would turn up only to milk California at fundraisers, this year there have been frequent campaign visits by all the leading contenders for the White House. They know that hundreds of convention delegates are at stake – more than a fifth of the total needed to win the Democratic nomination and 15 per cent of the number that must be reached by a Republican.

Polls have long suggested that Mrs Clinton and Mr McCain enjoy double-digit leads in the Democratic and Republican races but with delegates being awarded proportionately Mr Obama and Mr Romney cannot afford to give up. Surveys also suggest that more than one in three voters may change their minds before election day and the most recent poll reflects Mr Romney and Mr Obama’s renewed momentum. “The race is getting more fluid and California has a certain restless quality,” said Jerry Brown, a former Democratic governor.

Mrs Clinton will be based here for much of the next five days. She has bought the most advertising slots while focusing heavily on the economy and wooing Latino voters, who account for perhaps a quarter of the Democratic electorate. Surveys suggest they support her by a margin of two to one against Mr Obama. She has more than 10,000 volunteers, key endorsements from black and Hispanic politicians, as well as the backing of the United Farmworkers’ Union.

Mr Obama, who was speaking at a rally in Los Angeles yesterday, has sought to build up a grass-roots movement which worked so well for him in Iowa and South Carolina. His campaign, heavily reliant on telephone and street canvassing, has established around 700 microgroups in the state.

On the Republican side, Mr Romney was campaigning in Long Beach, Fountain Valley and San Diego but – even as a multi-millionaire – appears to have balked at the cost of buying a TV advertising blitz which has been his weapon of choice in other states.

Aides say that he is concentrating on the more conservative districts in the interior where he will seek to depict Mr McCain as a liberal on immigration, a hot issue for a state with millions of undocumented workers.

Mr McCain attended a morning fundraiser in San Francisco before flying to Los Angeles to pick up the endorsement of the California Governor Arnold Schwarzenegger in Los Angeles. He is likely to attract the bulk of his votes from the coastal region, as well as districts with a high proportion of military veterans. But Independent voters, who have backed Mr McCain strongly in previous elections, are barred from the Republican contest and may skew towards Mr Obama.

California has not had such attention since Robert Kennedy won a dramatic primary against Eugene Mc-Carthy 40 years ago before being assassinated as he celebrated victory at the Ambassador Hotel in Los Angeles.

Edward Kennedy, his last surviving brother, will today speak at a rally in the same city to support Mr Obama – whose bid to be America’s first black president and message of change have inspired frenzied excitement. Having waited for so long, California will next week once more be the scene of another primary election pregnant with historic possibilities.

For the anoraks

A rule change by the California Republican Party has changed how candidates must campaign in the Golden State. In the past, Republican candidates who received the most votes statewide would capture all of California’s 173 delegates. It was winner-take-all. Now delegates are apportioned by the winner in each of the state’s 53 congressional districts. Campaigns must now work out how to get the most delegates, district by district. Each district is worth three delegates – no matter how small it is – meaning that candidates are targeting areas they would usually ignore in a general election

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