Biden’s support is driven by older Democrats and by nonwhite Democrats — two groups that aren’t always well-represented on social media or in other forums that sometimes dictate the conventional wisdom about the candidates. Biden had 50 percent of nonwhite voters in the CNN poll, well ahead of Sanders’s 14 percent. In Morning Consult’s poll, Biden polled at 43 percent among black Democrats, compared to Sanders’s 20 percent. Biden had 46 percent support from Democrats age 50-64 in CNN’s poll and 50 percent support from those 65 and older.

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What that means is that it’s time to take stock of the three candidates who have clearly fallen from their peak (so far) in the polls — Sanders, Harris and O’Rourke. You might think that on the basis of his current polling, Sanders remains in a better spot than the other two. However, he’s also much more of a national brand name. And as I wrote last week — and as you can see from the chart — polling at 20 percent is not all that strong a position for a candidate with near-universal name recognition. Sanders, however, polled at just 16 percent in the average of the four national polls released on Tuesday. And he was at only 12 percent in New Hampshire, which should be one of his strongest states. Sanders can win — he’ll raise a lot of money, he came from way far back last time, and he’d likely benefit from scenarios where the field remains divided. But given his name recognition, those polling numbers put him right at the divide between someone whose campaign is going well and someone whose campaign is going poorly.

Harris and O’Rourke are not as widely known as Sanders, and they still have reasonably good favorability ratings and plenty of cash on hand, which suggest that they have upward potential if and when the media’s attention turns to them again. But it’s become harder to make the case that they’re on the lead lap with Biden, especially for O’Rourke, who is competing against a field that’s overstatured with white male candidates and whose polling has fallen further than Harris’s.

Buttigieg doesn’t have any reason to be unhappy; given his low name recognition, polling in the mid-to-high single digits — sometimes higher than that, especially in polls of Iowa and New Hampshire — is a pretty decent position. But if you were expecting a further immediate surge into the teens or beyond — and I sort of was — it isn’t as clear now whether that’s coming. Instead, Buttigieg will need to work to expand his support beyond his initial coalition of highly educated white voters and survive media coverage that’s both less plentiful and more skeptical than it was initially.

But Warren is in an intriguing position. Warren’s the candidate who we thought might have the least overlap with Biden and therefore would be least hurt by his entry into the race — and the polling seems to bear that out. Although both candidates are broadly within the Democratic mainstream, she’s toward the left half and he’s toward the moderate half. She’s a woman and he’s a man, obviously. His case rests heavily on electability and big, abstract, meat-and-potatoes themes; she appeals to voters on the basis of her highly detailed policy proposals. Her base is college-educated whites; his is non-college-educated white voters and black voters. Biden and Warren have directly clashed over issues such as bankruptcy laws.

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