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Our Final Forecast For The South Carolina Primary

With South Carolinians headed to the polls, it’s time to freeze FiveThirtyEight’s forecast and take a final look at the state of the Democratic nomination race before we get the results from the “First in the South” primary. This means we won’t be adding any new information to the forecast or updating the candidates’ odds until South Carolina’s results are available. Luckily, South Carolina uses a primary, so we probably won’t have to wait days to get near-complete results.

First, here’s what our forecast says about the candidates’ overall chances of winning a majority of pledged delegates. The single most likely outcome is actually that no candidate wins a majority by the time voting finishes on June 6 in the Virgin Islands. There’s about a 1 in 2 (52 percent) chance of that happening. Among the candidates, Sen. Bernie Sanders has the best chance of winning a majority of pledged delegates, with around a 1 in 3 (32 percent) shot. After Sanders comes former Vice President Joe Biden, who has about a 1 in 6 (16 percent) chance. Rounding out the remaining contenders, former New York Mayor Michael Bloomberg has a 1 in 100 (1 percent) chance while both Sen. Elizabeth Warren and former South Bend, Indiana, Mayor Pete Buttigieg have less than a 1 percent shot.

As for the South Carolina primary, our forecast views Biden as the heavy favorite, to the tune of a 29 in 30 (97 percent) chance of claiming first place. The only other candidate who has a meaningful chance of winning is Sanders, who has a 1 in 30 (3 percent) shot — a Sanders win is plausible, but it would register as one of the bigger polling upsets we’ve seen in a primary. South Carolina is only the fourth contest in the 2020 Democratic primary, but Biden’s win probability there is the highest any candidate has had when we’ve frozen our forecast ahead of the early states, surpassing Sanders’s roughly 6 in 7 (85 percent) chance of victory in Nevada last weekend.

Biden’s rise in South Carolina happened very quickly — a week ago, he had a 2 in 5 (40 percent) chance of winning, slightly behind Sanders’s almost 1 in 2 (46 percent) chance. Then a plethora of post-Nevada polls came out showing Biden leading in the state by double-digit margins.

As for the last batch of South Carolina polls, they continued to give Biden a clear lead, though there was disagreement over just how big an advantage he has. And Biden’s margin — if he does win — will likely matter, influencing how the media views his win and thus affecting how voters react to it heading into Super Tuesday. That is, a narrow victory could look bad for Biden, especially now that he has a sizable lead in the polls, while a bigger margin could spark a “comeback” narrative. So let’s take a look at those final South Carolina polls (with the most recent surveys listed first):

  • The last poll we got from South Carolina comes from AtlasIntel, which found Biden at 35 percent and Sanders at 24 percent. The only other candidate in double digits was Steyer with 12 percent, while Buttigieg had 8 percent, Warren 7 percent and Klobuchar 4 percent. But before we put a poll in our model, we adjust for a pollster’s house effects — how well or poorly a candidate usually does in the pollster’s poll — as well as the national trend. In this case, AtlasIntel has been a little bearish on Biden and bullish on Sanders, so Biden shifts up to 36 percent and Sanders slides to 22 percent after our adjustments.
  • Republican pollster Trafalgar Group took a look at the Democratic race and found Biden leading Sanders by a nearly two-to-one margin, 44 percent to 23 percent. Steyer and Buttigeg were far behind at 11 percent and 10 percent, while both Klobuchar and Warren had 6 percent. Once we account for house effects and the national trend, the poll goes into the model with Biden up 19 points.
  • On Thursday evening, Data for Progress put out a new poll that found Biden leading Sanders by 9 points, 34 percent to 25 percent. The only other candidates in double digits were Steyer and Buttigieg, who both had 13 percent. Data for Progress has been pretty accurate so far this cycle, so it’s notable it found a somewhat smaller lead for Biden than other pollsters. But its polls have also tended to find better results for Sanders than some other pollsters — after adjusting for house effects and the national trend, this poll enters the model with Biden leading Sanders by roughly 13 points.

We also got five new national surveys, which collectively may be reassuring to Sanders’s chances beyond South Carolina. He led in each survey, though the polls showed varying degrees of competitiveness, as Sanders’s margin ranged from 6 to 13 points. Here are the latest nationwide polls (again with the newest surveys listed first):

  • On Friday night, Change Research published a national poll conducted Tuesday through Thursday showing Sanders way out in front with 40 percent, and Warren in second (!) with 20 percent. They were followed by Buttigieg at 14 percent, Biden 9 percent, Klobuchar 8 percent, Bloomberg 3 percent and Steyer 2 percent. Obviously showing Warren in second makes this survey a bit of an outlier, but Change Research has tended to find better results for Sanders and worse results for Biden than other pollsters. After it’s adjusted for house effects, Sanders is at 35 percent, Warren is at 16 percent, Biden is at 12 percent, Buttigieg is at 10 percent, Klobuchar is at 8 percent, Bloomberg is at 6 percent and Steyer is at 2 percent.
  • On Friday afternoon, Morning Consult released a national poll conducted since Tuesday’s debate in South Carolina. The survey found Sanders ahead of Biden by 12 points, 33 percent to 21 percent, though it showed Biden gaining the most ground after the debate. The other candidates in double figures were Bloomberg at 17 percent, Warren at 11 percent and Buttigieg at 10 percent. Once we adjust for house effects, this poll goes into the model as Sanders 29 percent, Biden 17 percent and Bloomberg 15 percent, with the other candidates seeing little change.
  • A Yahoo News/YouGov national poll on Friday found Sanders with about half as large a lead compared to the Morning Consult survey. Sanders had 27 percent, Biden 21 percent, Warren 18 percent, Bloomberg 14 percent and Buttigieg 10 percent. YouGov usually has very good numbers for Warren and worse ones for Bloomberg, so the model treats this as a 15 percent result for Warren and 16 percent for Bloomberg.
  • Also on Friday, SurveyUSA/FairVote put out a survey that had Sanders up 7 points, 28 percent to 21 percent, over both Biden and Bloomberg, who tied for second. The only other candidates close to 10 percent were Buttigieg and Warren, at 9 and 8 percent, respectively. Because SurveyUSA tends to have better numbers for Biden and Bloomberg, their totals were docked slightly in our model, with Bloomberg getting 19 percent and Biden 18 percent. An additional wrinkle with this poll was the use of ranked-choice voting by respondents, and after whittling the field down to two candidates, Sanders led Biden 51 percent to 49 percent.
  • Fox News released a survey on Thursday that found Sanders with a 13-point lead over Biden, 31 percent to 18 percent, with Bloomberg close behind at 16 percent. Additionally, Buttigieg was at 12 percent and Warren at 10 percent. After taking into account house effects, Biden went into the model with 16 percent, with small changes for everyone else.

Although Biden is in a good position to win South Carolina, these national polls suggest that he still has work to do if he wants to catch up to Sanders across the country. Looking ahead to Super Tuesday, when many big states vote, the Biden campaign’s lack of investment in those states compared to other campaigns (including Sanders’s) could make building on a South Carolina win more challenging. Biden may really need a huge win in South Carolina to overcome a resource disadvantage in the states that vote just three days later.

But heading into tonight, Biden is the odds-on favorite to win the Palmetto State. There’s a chance he doesn’t finish first there, but it looks like the main thing to watch for will be his margin of victory. The polls disagree about what we might expect on that front, and the scope of Biden’s expected win could affect how much it helps him going forward. With all eyes on South Carolina tonight, make sure to join us on our live blog as we analyze the results as they come in and ponder what they mean for the Democratic nomination race going forward.


South Carolina Could Be Just One More Step Toward A Contested Convention

Geoffrey Skelley is an elections analyst at FiveThirtyEight.

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