US:As Super Tuesday nears, the battle for votes is intensifying, writes Denis Stauntonin Washington
As Hillary Clinton and Barack Obama battle for votes in South Carolina this week, the Democratic race is dividing along the lines both candidates say they want to avoid - race and gender.
Mrs Clinton owed her victory in Nevada to the overwhelming support she received from two groups - Hispanic voters and women - in a caucus that saw four out of five black voters choosing Mr Obama. Women were also the key to Mrs Clinton's win in New Hampshire and she is depending on their support to make inroads into South Carolina's African-American vote.
The breakdown of Hispanic support in Nevada - two to one in Mrs Clinton's favour - is a worrying sign for Mr Obama as the race moves towards Super Tuesday on February 5th, when Hispanic voters could play a decisive role in key states, including California. That state accounts for a fifth of the delegates to the Democratic national convention in August. On that day, 24 states will hold primaries or caucuses.
Mrs Clinton's Nevada win has also increased pressure on Mr Obama to win in South Carolina, where he currently enjoys a double-digit poll lead. Nevada has emboldened the Clinton campaign to make a last-ditch effort to take South Carolina, sending former president Bill Clinton to canvass door to door in black neighbourhoods.
As both campaigns settle in for a long struggle beyond February 5th, the Democratic race has become a battle for delegates, which are awarded proportionately - candidates who lose a primary can still pick up delegates.
This is why Mr Obama is campaigning hard in delegate-rich New York despite the fact that Mrs Clinton is likely to win in her home state. The former first lady is also fighting for every vote in Mr Obama's back yard of Illinois.
Mrs Clinton lost to Mr Obama in Iowa partly because her campaign underestimated the turnout, a mistake not repeated since.
In New Hampshire and Nevada, Mrs Clinton's ground game outpaced Mr Obama's, so that she won the caucuses even in most of the Las Vegas casinos where Mr Obama had the support of a powerful union.
The emergence of the economy as the campaign's biggest issue plays to Mrs Clinton's strength as a candidate focused on bread-and-butter issues with an unrivalled grasp of policy detail. At last week's debate in Las Vegas, she sounded like the class swot as she spoke with confidence about sovereign wealth funds and the complicated financial instruments at the heart of the subprime mortgage crisis.
At a rally later that evening, however, she was equally comfortable talking about the price of milk and eggs - two commodities the former first lady is unlikely to have shopped for in person.
By contrast, Mr Obama appears uneasy with the nuts and bolts of policy, especially on the economy. At two events last week he made simple mistakes, confusing a tax increase with a tax cut and getting into a muddle as he sought to explain his plan to safeguard the social security system.
On the Republican side, the focus on the economy should benefit former Massachusetts governor Mitt Romney, the only candidate with a solid background in business. Mr Romney won last week's primary in his home state of Michigan by promising to revive the motor industry. He is campaigning as a manager who can apply his experience of turning around ailing companies to rescuing the troubled US economy.
Mr Romney and Arizona senator John McCain are currently the strongest candidates as they enter a four-way race in Florida with former New York mayor Rudy Giuliani and former Arkansas governor Mike Huckabee.
Losing narrowly to Mr McCain in South Carolina was a blow to Mr Huckabee, who was counting on grass-roots support from evangelical Christians to outflank Mr McCain's superior funding and organisation. Mr Huckabee fared well among white born-again or evangelical Christians but among other voters, Mr McCain had an overwhelming advantage - about four in 10, nearly three times Mr Huckabee's support.
Mr McCain remains a suspect figure to many conservatives, some of whom accuse him of courting the support of the media by opposing his own party's base on everything from tax cuts to immigration.
Influential conservative talk radio hosts, led by Rush Limbaugh, have been loud in their condemnation of both Mr McCain and Mr Huckabee as they talk up Mr Romney as the most conservative candidate with the best chance of winning in November.
Mr Giuliani remains the wild card in Florida, where he is hoping for his first victory after opting out of most of the early contests. The former New York mayor believes that if he wins in Florida he will be the front-runner on Super Tuesday, when big states like New York and California could swing in his direction.
Unlike the Democrats, Republicans have a winner-takes-all primary system, so that in most states, the candidate who wins the primary claims all of that state's delegates to the convention that will choose the party's presidential candidate.