The muddled race to secure the Democratic nomination for US president enters a new phase this weekend as voters in the western state of Nevada gather to show their preference for one of the seven candidates still in the race.

With two contests behind them, the candidates fanned out across the state ahead of the vote in an effort to convince caucus-goers that they were best suited to take on President Donald Trump in the November general election.

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Speaking at a rally Friday, the race's current frontrunner, Bernie Sanders, focused on encouraging voters to participate in the caucuses.

"You know, if you cannot win an election based on your ideas and your ability to convince people to vote for you, you should not run for office," Sanders said. "But many cowards out there who can't win an election on their ideas are trying to suppress the vote all over this country."

High-stakes contest

The contest in Nevada is being billed as the first one in a state that more accurately reflects the ethnic makeup of the US as a whole. Unlike Iowa and New Hampshire, where more than 90 percent of voters are white, Nevada counts a sizable contingent of minorities, with 30 percent of the population describing themselves as Latino and 10 percent African American.

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The stakes could not be any higher for the remaining Democratic candidates.

Polls released in the final days leading up to the vote showed Sanders firmly out in front of his more moderate challengers, with the support of 30 percent of voters compared to about 15 percent for Joe Biden, his closest competitor. Sanders's lead among Latino voters was even higher, standing at 33 percent in one poll conducted by the Spanish-language Univision television network.

Poor performances in the first two states by Biden, the former front runner, sent his national poll numbers plummeting and spooked the big donors who had been backing him. His campaign manager, Greg Schultz, told reporters on a conference call that Biden is banking on at least a second-place finish in Nevada.

Minnesota Senator Amy Klobuchar and former South Bend, Indiana, Mayor Pete Buttigieg are seeking to capitalise on the momentum from strong showings in New Hampshire. Klobuchar finished third in New Hampshire and Buttigieg finished second, just over one percentage point behind Sanders. Nevada will be the first test, however, of whether the two can broaden their base of support and appeal to voters of colour.

Elizabeth Warren's campaign got a boost from Wednesday night's debate, which set a television ratings record, where she went on the offensive and attacked the newcomer on stage, billionaire Michael Bloomberg, for trying to "buy" the nomination. Her performance prompted an outpouring of financial support -$5m in the 24 hours after the debate - and breathed new life into a campaign that had been flagging since disappointing results in both Iowa and New Hampshire.

Unusually, Bloomberg is not even on the ballot in Nevada. The former New York City mayor has opted to sit out the first four contests and concentrate his efforts on delegate-rich Super Tuesday. His campaign spent some $7m a day during January; $464m in total since he launched his effort in December.

The other billionaire in the race, Tom Steyer, is polling in fifth place in Nevada, while Hawaii's Tulsi Gabbard, is polling below two percent.

Potential delay

After the disastrous caucuses in Iowa, during which results were delayed for days by software snafus, Democratic leaders have been keen to make it clear that they learned their lesson. Nevada officials scrapped plans to use the same software used in Iowa, flooded the state with staffers to help out, and set up a 200-person call centre to intake results. Even then, officials warned, the outcome could be delayed.

"We're going to do our best to release results as soon as possible, but our North Star, again, is accuracy," Democratic National Committee Chair Tom Perez told reporters earlier in the week.

This year, for the first time, party officials opened up the otherwise restrictive caucus process and allowed early voting to boost turnout and interest. The change had its intended effect. Officials said around 75,000 people turned out to vote during a four-day window early in the week, some of them waiting more than three hours to do so, which is just shy of the 84,000 people who turned out to vote during the 2016 process.

Nevada has a total of 48 delegates up for grabs, 36 of which will be doled out based on the results of Saturday's vote. Heading into the competition, Buttigieg was ahead in the race for delegates, with 23, compared to Sanders' 21.