(CNN) Former Vice President Joe Biden and Sen. Bernie Sanders of Vermont will stand at center stage in Tuesday night's CNN/Des Moines Register Democratic presidential debate.

The debate, which will air on Tuesday at 9 p.m. ET exclusively on CNN, is the final face-to-face gathering of the candidates before the February 3 Iowa caucuses. CNN's Wolf Blitzer and Abby Phillip, as well as The Des Moines Register's Brianne Pfannenstiel, will moderate the debate at Drake University in Des Moines, Iowa.

The podium order was based on an average of qualifying polls released in January. Candidates with the highest averages were placed in the center of the stage.

In order to qualify for the debate, candidates needed to meet polling and fundraising minimums, which had been raised from the previous debate -- which took place in December -- by the Democratic National Committee. Candidates were required to have received 5% in at least four DNC-approved national or early-voting-state (Iowa, New Hampshire, South Carolina, Nevada) polls, or 7% in two early state polls. Candidates also needed to have received donations from at least 225,00 unique donors and a minimum of 1,000 unique donors per state in at least 20 states.

Read More