The field has narrowed with three Democratic presidential candidates taking the stage Saturday evening in Des Moines, Iowa, at Drake University. The debate begins at 9 p.m. EST and will feature former U.S. Secretary of State Hillary Clinton, Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O’Malley.

The weekend CBS/KCCI/Des Moines Register debate will be live-streamed for free online and can be viewed here. CBS will also air the debate on affiliate radio stations and you can listen by clicking here. The debate also will be available through the CBS News mobile app.

The debate is scheduled to last two hours. CBS has said there will be no opening statements. With only three candidates onstage, each candidate is expected to be able to speak for longer periods of time. The format allows for a one-minute response to questions and 30 seconds for rebuttals and follow-ups. Candidates will be given one minute each for their closing statements.

While the Republican presidential debates have featured a full stage of candidates, two Democrats have dropped out since the party's first debate: former Rhode Island Gov. Lincoln Chafee and former Virginia Sen. Jim Webb. In addition, Vice President Joe Biden ended months of speculation by declaring he would not seek the presidency.

The debate will be moderated by “Face the Nation” anchor John Dickerson, who said he plans to focus on economic matters, such as income inequality and wage fairness.

CBS has partnered with Twitter for this debate and has said it will take viewer questions that use the hashtag #DemDebate. This is the first debate in which Twitter will be an official participant. Social media site Facebook has been associated with one Democratic and one Republican debate.

The next Democratic debate was scheduled to take place Dec. 19 in Manchester, New Hampshire.