Voters in 14 states will head to the polls or will caucus to choose their party's nominee for president.
Democrat Hillary Clinton and Republican Donald Trump are predicted to sweep delegates on 1 March.
Sanders needs strong showing to keep presidential bid alive.
Polls put Clinton ahead in next round when 11 states vote.
Sanders needs black voters to win the nomination, but he's struggling to prise them from Hillary.
The Democrat's presidential candidate was speaking ahead of the latest primary in South Carolina.
The figure comes complete with signature slouch, open mouth and accusatory pointed finger.
Donald Trump was once upon a time a part-time star in professional wrestling
Voters in 14 states will head to the polls or caucuses to choose their presidential nominees on 1 March.
Jeb Bush, Chris Christie and Carly Fiorina all dropped out after outperforming Carson.
Former PM likens Vermont senator's presidential campaign to Jeremy Corbyn's election as Labour leader.
There was a significantly lower voter turnout compared to 2008, Nevada Democratic Party officials say.
The insurgent Vermont senator still has a lot to do elsewhere if he is to overtake Clinton.
Exit polls gave Trump 32.5% of the vote, placing him 10% ahead of nearest rival, Marco Rubio.
Republican voters head to the polls on 20 February while Democrats will have to wait until 27 February.
The Vermont senator studied in Chicago from 1960-64 and was arrested on 12 August 1963.
Democrat rivals urge Nevada voters to head to the polls on February 20.
Trump made the remarks at a rally in Tampa, Florida.
The candidates are meeting for the first time since Sanders' landslide victory in New Hampshire.
Rhodes Must Fall failed, Barbie and Beyonce won - which sells merchandise?
Larry Sanders, brother of Bernie, is trying to stop NHS privatisation as one of his major tasks.
Republican candidate says United States infrastructure lags behind other countries and needs to be developed.