las vegas for the lesser known candidates like former mt. governor martin o'malley, the debate is a chance to find support that has so far alluded them. but one of the biggest potential challengers to clinton and sanders won't even be there. vice president joe biden is still 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, you know, wrestling with these issues, i'm sure that for him he's saying to himself i could do a really good job. >> now, another reason why these new cnn/orc poll numbers have some democrats more bullish on hillary clinton has to do with the black vote in south carolina. she gets 59% of this key voting demographic for democrats if joe biden is in the race. but check this out take joe biden out of the race she pops all the way up to 84%. bernie sanders only at 7%. he's really struggled to speak to black voters in a way where