Go deeper with analysis from SurveyMonkey: "For now, the most consistent finding from our results is that the Democratic candidates do best either among all registered voters or among those who say they are either absolutely or at least somewhat certain to vote."
"Republicans do consistently best in a probabilistic scenario based on modeling the 2014 election, not surprising since that election featured a considerable GOP turnout advantage. Beyond that, the outlook on how much Democrats might benefit from turnout remains hazy."