Des Moines, Iowa — Democrats are preparing for what could be their most contentious debate Tuesday as the leading candidates look for a way to break out of the crowded top tier less than three weeks before the state’s caucuses kick-start the presidential nomination process.

The debate is being held on the Des Moines campus of Drake University and will be televised on CNN from 9 to 11 p.m. The debate is the final face-to-face gathering before the Feb. 3 Iowa caucuses.

CNN’s Wolf Blitzer and Abby Phillip, and The Des Moines Register’s Brianne Pfannenstiel, will moderate.

The debate will stream live, without requiring log-in, on CNN.com; across mobile devices via CNN’s apps for iOS and Android; via CNNgo apps for Apple TV, Roku, Amazon Fire, Chromecast and Android TV; and at DesMoinesRegister.com.

CNN.com contributed to this report.