I wonder if Biden is syphoning more votes from Hillary or Sanders and if just syphoning votes to make it a three way race will sink Sanders.

"Clinton, once the prohibitive front-runner, is now the top choice of 33 percent of registered Democrats and those who lean Democrat, the poll shows. Biden places second with 25 percent and Vermont Senator Bernie Sanders is at 24 percent.""Clinton is better liked by women than men—74 percent to 64 percent—while Biden's favorability is closer to gender-neutral, with 81 percent for women and 79 percent for men. The survey also found those who are married or have children under the age of 18 were more likely to give Biden favorable ratings than Clinton."

-http://www.bloomberg.com/politics/articles/2015-09-23/bloomberg-poll-joe-biden-now-top-presidential-choice-for-1-in-4-democrats