http://www.slate.com/articles/news_and_politics/politics/2015/08/joe_biden_presidential_run_why_it_s_a_bad_idea.html

Democrats being Democrats, it’s no surprise that some are skittish about Hillary Clinton’s campaign, which has been hit with scandals and weak numbers in key swing states. To these Democrats, Clinton isn’t a strong bet, and worse, there isn’t a strong alternative. Bernie Sanders? Popular, but too far to the left to unify a broad and diverse national party. Martin O’Malley? Not exciting.