Excuse me but is not the fact of the Obama administration--the first black President--who choose and presided over the most diverse administration in US history--was this phenomenon not the result of "influence by the left" on the Democratic party? I can prove the party has been historically influenced by the left in many instances whereas you would not be able to support your claim that it never has been. 
To the extent the Clintons have embraced conservative economic policies it is a function of their utility--that is--getting elected. In an political atmosphere such as currently prevails in the US congress--where Republicans have tried time and again to eliminate food stamps, eliminate the earned-income tax credit and various other attacks on the poor and middle class--where is the space for Bernie-style socialism? We barely got Obamacare. Would you be willing to bet your worldly possessions on Sanders' ability to accomplish what he claims he will?  I doubt it.