I dont think Biden would beat Hilary, and I do not think she is by any means a slam dunk. All you have to do is go back to 2008 when Obama came out of nowhere and cleaned her clock. Truth is she is a terrible campaigner, and she could lose the nominatioon and/or the general election. Personally I think Bill is more interested in her getting the job than she is. Like her or not, she has put in her entire adult life in public service..from the Watergate committee, to First Lady of Arkansas, to Firt Lady of the U.S. to United States Senator, to Presidential candidate to Secretary of State. She has every right to sit back and smell the flowers.
I recently had the same discussion - Hillary is an awful campaigner. Especially considering that she is married to one of the best campaigners of the past 30 years. Plus she is getting old and will have a tough time convincing some voters because of her age.
Biden is in much the same position Al Gore was in heading into 2000. Gore was trying to distance himself from the Clinton affair scandal, which is not as bad as Biden trying to get out from the poor presidency of Obama. Gore was a vanilla personality and didn't use Clinton enough IMO, but Biden is going to be associated with many of the failures of his boss' term, from health care to Benghazi.
