Honestly the Dems forgot Bill Clinton's lessons and reverted to pre-Clinton liberalism especially during Obama's second term. The best winning combination for Dems would have been Hillary's economic policies and Mike Huckabee's social policies.
Mike Huckabee's social policies are enormously unpopular so it's hard to see why that would have been helpful.
In fact after reading over them a bit they are downright deranged. No candidate from either party could ever be elected running on such an extremist social platform.
http://www.ontheissues.org/Mike_Huckabee.htm