A memo from Tulchin Research, pollsters for the Sanders campaign:
With the second half of the 2016 presidential primary season upon us, Democrats must now more than ever seriously consider which prospective nominee – Bernie Sanders or Hillary Clinton – is best positioned to lead Democrats to victory in November. Public polling has produced an overwhelming body of evidence that Bernie Sanders is that candidate. Data has consistently proved this point over the past six months and recent polling data re-affirms this finding at an unprecedented level. CONT. – pdf
Ben Tulchin, Ben Krompak & Kiel Brunner, Tulchin Research
Recent polls: Presidential election