The Democratic presidential hopefuls will face off for the fourth time this weekend. Unlike previous debates where there are multiple rounds involving several candidates, Sunday's event will only have three participants: Vermont senator Bernie Sanders, former Secretary of State Hillary Clinton and former Maryland governor Martin O'Malley. The debate will also be their final face-off prior to the Iowa caucuses and the New Hampshire primary.

The latest presidentiable to qualify for the gathering is O'Malley, thanks to a review of recent poll percentages. According to NBC, who will co-host the event, candidates need to reach five percent in recent national polls or surveys of Iowa, New Hampshire, or South Carolina to qualify.

O'Malley's weakening poll numbers threatened to keep him from joining Sanders and Clinton on stage, NBC News noted. Poll results released this week found that the former governor enjoy five percent support among likely caucus goers in Iowa, well behind Clinton and Sanders who got 48 and 45 percent, respectively.

Aside from the said news channel, the South Carolina Democratic Party and the Congressional Black Caucus Institute will also be co-hosting the debate. It will take place on Sunday at the Gaillard Center in Charleston, S.C. and the coverage will air live on NBC at 8:00 p.m ET. However, the debate itself is slated to begin at 9 p.m. ET. Those who already have plans on Sunday night can watch an encore run on MSNBC at 11 p.m. ET.

The main moderator during the debate will be NBC Nightly News anchor Lester Holt. Andrea Mitchell, the news outlet's chief foreign affairs correspondent, will also ask questions.

Those who do not have access to local NBC station can keep tabs on the Democrats' showdown by checking it out online on NBC's YouTube channel. People watching the debate on the video-sharing site can also submit their questions to the candidates.

It will also be possible to watch the Democratic debate on the go. Android and iOS users can download the NBC News app for free. These apps will provide a free stream of the debate as well. NBC notes that the official hashtag for the event is "#DemDebate" so Internet users can keep track or contribute to social commentary.

The broadcast network is also keen on ensuring that the debate will be viewable on as many types of screens as possible so it is making the event available through the Amazon Fire TV, Roku, and Apple TV players. Those who have Roku connected to their TV sets can watch it through the NBC News App, while Apple TV users can search the tvOS App Store for "NBC News."