after this moment went viral. >> i don't want to see us go backwar backwards. >> when it was over, i just felt drained. i didn't feel anything other than that. i didn't realize it was going to be a big deal. >> tuesday night the five democratic contenders will take the stage for the lesser known candidates like former maryland governor martin o'malley, it's a chance to find support that eluded them but one of the biggest potential challengers to clinton and sanders won't be there. vice president joe biden is weighing whether to run. on cbs president obama said he understands why biden might get in. >> if you're sitting right next to the president in every meeting and wrestling with these issues, i'm sure for hill he's saying to himself, i could do a really good job. >> brianna joins me now from the debate stage. how are they preparing for the debate?