Democrats Square Off in First 2016 Presidential Debate

— -- The five Democratic candidates making a bid for the White House -- Hillary Clinton, Bernie Sanders, Martin O'Malley, Jim Webb and Lincoln Chafee -- will be on the debate stage tonight at the Wynn Las Vegas.

Tonight marks Hillary Clinton's first return to the debate stage in seven years.

CNN Anchor Anderson Cooper will moderate the debate. Coverage begins at 8:30 p.m. Eastern time and the debate starts at 9:00 p.m. Eastern.

Keep checking back for updates from our ABC News politics team as the five candidates prep for the debate, when the candidates take the stage, and when they take on the spin room.