We looked at this a bit back in May, when the Sanders phenomenon was first emerging. But it's worth revisiting now that he has surged.
If you extrapolate Census turnout estimates into 2016, we can figure that some 137 million will turn out to vote next year. That's maybe a bit high, but it doesn't really matter. It gives us a figure to work with.
In September, Gallup did its regular assessment of how Americans identify politically. The number who said they were Democrats or Republicans was the same, 27 percent. The rest were "independents," though a number of those independents leaned toward one party or the other. (This is not uncommon at all.)
Those partisanship figures change a lot, but let's use them as-is. If we apply those percentages to the 137 million people that vote, assuming (unfairly) that partisans vote at even rates, we get about 37 million people in each party, about 25 million Republican-leaning independents and about 23 million Democratic-leaning ones.
If we then apply polling averages to those numbers, we get a look at how many people (generally) support each candidate. Note that the ratios below don't change even if the numbers of voters change; it's a percent of a percent. But the upshot is this: More Americans support Sanders than Trump.
There are other surprises: More Americans support Jim Webb than Rick Santorum! More Americans support Lindsey Graham than Martin O'Malley!
This is not hard-and-fast and relies on numbers that have a decent margin of error. But we can also simplify the argument. About half the country is Democratic and about half is Republican. Sanders gets about 25.1 percent of Democratic voters; Trump gets 23.7 percent of Republican ones. Ergo: America is Bernie Country more than it is Trumpland.