This polling data suggests that Bernie Sanders has a huge appeal to Independent voters, as Bernie Sanders has gained a lot of traction reaching across party lines this election cycle.
The latest polling data for Bernie Sanders comes from a study from Quinnipiac from the time frame of 12/16-12/20. This poll shows Bernie Sanders with a HUGE lead on Donald Trump, ousting him by 13 points.
The data shows that if the election were Bernie Sanders vs. Donald Trump, that Bernie Sanders would get 51% of the vote compared to Donald Trump's lowly 37%.
The match-up between Hillary Clinton and Donald Trump does not go so well. This report comes from Rasmussen from the timeframe of 12/22-12/23. This data shows Hillary Clinton only winning by 1 point with 37% of the vote compared to Donald Trump's 36%
After analyzing both of these polls, you may notice that while Donald Trump remains in the high 30's in both polls (37% and 36%) that Bernie Sanders actually picks up 14 more points than Hillary Clinton (51% vs 37%).
One thing that Democratic voters will be looking for in a candidate in the primaries is electability in the general election. These polls indicate that Bernie Sanders is a lot more electable than Hillary Clinton in the general election and that he has a broader reach to independent voters.