1. Can she grow her base?

Vice President Biden remains the solid favorite among older voters, African-Americans and moderate to conservative Democrats. Sen. Bernie Sanders is still the leading candidate among younger voters. Since August, Warren has made some small inroads into those demographic groups, according to CNN polling. For example, Warren gained 9 points among those over 45-years-old, while both Biden and Sanders lost ground (Biden lost four points, Sanders lost three). But, among non-white voters (Biden’s core), Warren slipped two points and among 18-49-year-olds (Sanders voters), she gained just one point.