Hillary Clinton and Bernie Sanders go head to head this Saturday as Democratic voters in Nevada hold a caucus to choose their presidential candidate.

It is the third vote in the primary season, sandwiched between New Hampshire, where voters cast their ballots earlier this month, and South Carolina, where people will have their say on February 27. 

As David Usborne of The Independent explains, it is hugely important, especially for Ms Clinton. Here is why:

Bernie Sanders and Hillary Clinton are battling for voters ahead of a primary election in South Carolina

1. After a virtual tie in Iowa and a huge win in New Hampshire, the Vermont senator has steadily built momentum. He is keen to show that he can win the votes of not just white voters - who made up the majority of those voting in Iowa and New Hampshire - but from a more diverse population. 

2. Ms Clinton’s campaign has always considered South Carolina, where there are many black voters, and Nevada, where there is a large hispanic population, as her firewall against Mr Sanders’ surge. If she loses in Nevada, she could still win in South Carolina, but more questions would be asked about her chances of going all the way.

3. Polls have Mr Sanders and Ms Clinton neck-and-neck across the country. A Quinnipiac national poll scored Ms Clinton 44 to Mr Sanders 42. A CNN poll for Nevada put Ms Clinton on 48 points, with Mr Sanders on 47. A Public Policy Polling tally scored Ms Clinton 52 and Mr Sanders 35 in South Carolina. Essentially, everything is very close.

4. Ms Clinton has cast herself during her campaign as the person who not only has a record of achievement and experience at the very highest levels of government, but as someone who could win a general election against any Republican contender. But the more she endures defeats, the more the sense of “inevitability disappears and the more Mr Sanders’ claim to be a genuine national candidate gathers traction.

5. Just days after the South Carolina vote, around a dozen states hold their primary on March 1, so-called Super Tuesday. With states such as Alabama, Massachusetts and Colorado in play, there are large numbers of delegates to be won. It could be the day that decides the direction of the primary contest and the candidate seen to gaining momentum going in to Super Tuesday, may well find themselves well rewarded.