Wow! Bernie Sanders is nippin’ at Hillary Clinton’s heals in Iowa and New Hampshire. The latest polls show Bernie just 8 to 12 points behind Hillary among New Hampshire Democrats; in Iowa, one-third of likely Democratic caucus-goers say they prefer Sanders, compared to 52% for Hillary. Sanders has been drawing huge, wildly enthusiastic crowds just about everywhere he has campaigned.

I would bet that Hillary and her staff started out viewing Sanders’ candidacy as just a minor annoyance, maybe even a good thing, introducing an illusion of competition into what would otherwise be a boring non-contest for the nomination. But now, they see it as a serious challenge. How did that happen? How did a relatively obscure senator from Vermont–-an avowed socialist who is not even a registered Democrat–-come up so fast?

The plain fact is that Sanders is a tremendously appealing political personality. Speaking with obvious passion and outrage in his heavy New York/Jewish accent, he seems refreshingly different from most politicians: candid, unaffected and unafraid to alienate those big campaign donors.   And his outraged fulminations—about widening inequality, about the great power of special interests in Washington and the slide toward oligarchy that comes with the increasing role of big money in our politics—happen to coincide with the views of a very large number of Americans, and not just Democrats.

One recent poll, for example, found that 60 percent of Americans—including 75 percent of Democrats—believed that “the economic system in this country unfairly favors the wealthy.” Sixty-six percent of Americans believe that wealth should be more evenly divided, and, that it is a problem that should be addressed urgently. How address it? Among other things, about 79% of Americans believe that rich people don’t pay their fair share of taxes; sixty-eight percent of Americans– including 87 percent of Democrats–favor raising taxes on people earning more than $1 million per year.

So, Bernie’s populist message has great resonance among Americans these days, and particularly among Democrats. And he is an utterly credible messenger.   As Matt Yglesias explains, no mainstream Democrat—and that would of course include Hillary Clinton—can boast the same kind of credibility:

The Democratic Party stands for very different things than the Republican Party, but both parties are financed largely by very large checks from very wealthy individuals and the ability to cater to the sensibilities of some subset of America’s super-rich demographic is a crucial test of leadership for both parties.

Sanders stands outside that system. He’s managed to campaign and win in a small, cheap, and very liberal state without cultivating a following among the uber-wealthy and he’s happy to run a shoestring presidential campaign powered by small donors.

Sanders really is a unique phenomenon in American politics today, and therein lies his appeal.

But The NY Times’ Nate Cohn doesn’t see it that way. He thinks that the surge for Sanders in states like Iowa and New Hampshire is not likely to extend to other places where Democratic voters are more diverse and less liberal. Socialist Sanders, after all, is extremely liberal, but liberals are a minority even among Democrats. Cohn thinks Sanders will not be able to effectively challenge Hillary among moderate and conservative voters.

Cohn is a skillful and insightful political number cruncher, but I think he seriously underestimates the strength of the Sanders phenomenon. Cohn suffers from a common problem among pundits: he takes too literally the polls in which people are asked to say whether they are liberal, conservative or moderate. As I have pointed out before, political scientists have known for at least half a century that Americans tend to be symbolically conservative but operationally liberal. That is, they like the idea of conservatism in general terms, and will readily identify as conservative, but when you ask them concretely about specific policy issues, they will far more often reveal liberal views. Consider the poll data I cited earlier on inequality. They would suggest that 60% or more of American voters are solidly if not extremely liberal, but currently only about 24% will actually say they’re liberal if you ask them to label themselves.

Let’s consider another poll: 59% of Democrats say that they could vote for a socialist for president.   But how could that be, if only 44% of Democrats identify even as liberal? Clearly, a good number of self-described moderates and probably even some conservatives would consider putting a socialist in the White House. But that would be absurd, unless we acknowledge that those ideological identities people give to pollsters don’t mean nearly as much as Cohn thinks they mean.

Don’t get me wrong: I don’t believe that Sanders has a serious chance of winning the Democratic presidential nomination.   But I think that he has an appeal that conventional punditry tends to underestimate.  He’s going to make things interesting, not least for Hillary.