The go-to poll for the Iowa caucuses is the one conducted for the Des Moines Register by Iowa-based Selzer & Co. This year, the Register is working with CNN on its primary polling, a new iteration of which was released over the weekend. The results of that poll quickly shifted the discussion about the 2020 Democratic presidential polling: South Bend, Ind., Mayor Pete Buttigieg had taken a lead, earning 25 percent of the vote and a nearly double-digit lead over the next three candidates.

There have been a couple of other Iowa polls over the past few days that showed a tighter race. But those polls weren’t DMR-Selzer polls, so they didn’t attract quite the same level of attention. Plus, Iowa is the jumping-off point for the rest of the races, and wins there have shifted the rest of the primaries in past election cycles. A Buttigieg win, in other words, potentially shifts the math.

At least for a few days.

On Monday, you see, Quinnipiac University released a poll of its own from South Carolina. That poll may end up being more significant for Buttigieg. Not because it shows his strength, but because it shows a distinct weakness.

In South Carolina, Quinnipiac has former vice president Joe Biden leading easily, with Buttigieg in fourth place. Factoring in the margin of error, though, Buttigieg is essentially in a bunch tied for second, with a lot of daylight between Biden and the rest of the field.

There’s an immediate and obvious reason for that. In Quinnipiac’s poll, Biden gets 22 percent of the white vote compared with Buttigieg’s 11 percent. Among black voters, though, Biden gets 44 percent of the vote.

Buttigieg gets 0 percent. Not 10 percent; there’s no character missing. Zero. Warren’s support is lopsided toward white voters, too, but she at least gets some support from black voters in South Carolina.

Granted, there are more black voters in South Carolina than in other places. But there are more white voters in Iowa than in other places, which is part of the reason Buttigieg fares better there.

Last year, the Pew Research Center estimated that 59 percent of the Democratic Party was white, with black Democrats making up 19 percent of the total. In South Carolina in 2016, 61 percent of Democratic primary voters were black, according to exit polls, about 40 percentage points more than the party as a whole. In Iowa, 91 percent of the Democratic caucus voters were white, about 30 points more than the party.

The result of that difference between the two states is that Biden performs better than his national average in South Carolina and worse in Iowa. For Buttigieg, that’s reversed — though he does much better in Iowa than he does nationally and only moderately worse in South Carolina.

One factor that Buttigieg supporters will surely point to is that he’s much less well-known than other Democrats. More than half of black respondents in South Carolina said they hadn’t heard enough to have an opinion of him. The only candidate who was less well-known was Andrew Yang, and since awareness correlates to support, that can help explain the low support for Buttigieg.

The argument, then? Once Buttigieg is better-known among black voters, his numbers in South Carolina will improve.

Maybe. But Buttigieg’s favorability numbers actually aren’t that great in the state. While he’s less well-known than other candidates among black voters, he’s also more poorly received. Despite only about 4 in 10 black voters being familiar with Buttigieg, a higher percentage views him unfavorably compared with any other candidate who polls above 1 percent.

He’s viewed favorably on net. If we adjust his net favorability to look just at those with an opinion — a way of estimating support once people get to know a candidate better — Buttigieg’s numbers don’t improve that much. If he were known by every voter but maintained the same ratio of favorable-to-unfavorable views, his net favorability would be the lowest of the leading Democrats in the state.

Again, Iowa can shift things. Buttigieg emerging victorious in the state might make him seem much more viable to voters elsewhere and would certainly increase awareness of his candidacy. Stranger things have very much happened.

That brings us full circle, back to his needing to do well in Iowa. Yes, he’s leading in the DMR-CNN poll. But that’s one poll, and there’s still a lot of uncertainty and Iowa’s caucus process means that second-tier candidates have a better shot than they might elsewhere. Winning Iowa may be Buttigieg’s lower hurdle compared with South Carolina — but it’s still a hurdle he needs to get over.