Hillary Clinton’s campaign is now telling reporters that she is at risk of losing Iowa to Bernie Sanders in the February caucuses. One ought to view these stories a bit cynically: It almost always benefits a candidate to lower expectations in Iowa, and these warnings are often designed to activate lethargic supporters. At the same time, the campaign press loves stories that suggest it’ll have a competitive Democratic primary rather than a walkover.

But in this case, Clinton’s campaign is probably right: Sanders could win Iowa. He’s up to 30 percent of the vote there, according to Huffington Post Pollster’s estimate. What’s more, Sanders could also win New Hampshire, where he’s at 32 percent of the vote. Nationally, by contrast, Sanders has just 15 percent of the vote and has been gaining ground on Clinton only slowly.

One theory to explain these numbers is that Iowa and New Hampshire Democrats are early adopters of Sanders’s populist-left message. It isn’t a bad theory. These states have received the most intense campaign activity so far, and Sanders’s name recognition is higher among Democrats in Iowa and New Hampshire — perhaps about 70 percent or 80 percent, based on recent polls — than it is nationally. If the theory is true, Sanders’s numbers will improve nationally as Democrats in other states become as familiar with him as those in Iowa and New Hampshire are.

There’s another theory, however, that probably does more to explain Sanders’s standing in Iowa and New Hampshire, and it’s really simple. Democratic caucus-goers in Iowa and Democratic primary voters in New Hampshire are really liberal and really white, and that’s the core of Sanders’s support.

Sanders, who has sometimes described himself as a socialist, isn’t likely to do so well with moderate Democrats, of course. That’s a problem for him, since a thin majority of Democrats still identify as moderate or conservative rather than liberal. But Sanders has a few things working in his favor. The share of liberal Democrats is increasing — pretty rapidly, in fact — and those Democrats who turn out to vote in the primaries tend to be more liberal than Democrats overall.

What’s received less attention is that Sanders has so far made very little traction with non-white Democrats. The most recent CNN poll found his support at just 9 percent among non-white Democrats, while the latest Fox News poll had him at only 5 percent among African-American Democrats. (Fox News did not provide crosstabs for Hispanics or other minority groups.)

In Iowa and New Hampshire, that isn’t a very big deal. In 2008, 93 percent of Democrats who participated in the Iowa caucus were white, while 95 percent of those who voted in the New Hampshire primary were.

In fact, along with the Democratic electorate in Sanders’s native Vermont, those in Iowa and New Hampshire are as favorable to him as any in the country. In the chart below, I’ve listed the share of Democratic voters who identified as liberal, and as white, in the 39 states where the networks conducted exit polls during the 2008 Democratic primaries. Then I’ve multiplied the two numbers together to estimate the share of Democrats in each state who were both white and liberal.

I estimate that 54 percent of the voters in the New Hampshire Democratic primary were white liberals in 2008. That’s the second-highest figure in the country, after Vermont (59 percent). In the Iowa caucus, meanwhile, white liberals made up 50 percent; that put the state in a tie with Massachusetts for the third-highest percentage.

The percentage of white liberals isn’t so high in other early primary states, however. It’s just 29 percent in Nevada and 19 percent in South Carolina. The percentage is also low in high-population, delegate-rich states like California (26 percent) and Texas (17 percent).

Put another way, Iowa and New Hampshire aren’t representative of the more diverse electorates that Democrats will turn out elsewhere. It just so happens that the idiosyncrasies of the first two states match Sanders’s strengths and Clinton’s relative weaknesses.

Clinton performed well among Hispanic voters in 2008, and while her failure to win African-American votes was a central reason her campaign failed, she now has excellent favorability ratings among black voters that are nearly as high as Barack Obama’s. If Clinton begins to see her support erode among those groups, her campaign will have some real reason for concern. Otherwise, just as was the case throughout the 2008 campaign, the media will misconstrue voting patterns that occur because of demographics and attribute them to “momentum” instead.