The latest poll of South Carolina from NBC/WSJ and Marist finds Donald Trump losing considerable support in the last week. Trump currently leads Ted Cruz by 5 points, 28-23. One month ago, the poll showed Trump with a 16 point lead in the Palmetto State.
Marco Rubio and Jeb Bush are in a tight race for third on the eve of the vote. Rubio currently has 15 percent support, followed closely by Bush with 13 percent. John Kasich and Ben Carson are tied for a distant fifth with 9 percent each.
Other recent polling in the race continues to show Trump with a strong double-digit lead in the state. In the RealClearPolitics average of polls, Trump leads Ted Cruz in South Carolina by 14 points.
One key difference between the NBC poll and other public polls is in its estimation of the electorate likely to vote on Saturday. In other words, how much of the overall electorate will be comprised of evangelicals, moderates, conservatives, etc. Most public polling has not made this information available.
In a few polls where it is available, its estimates don’t match the traditional vote in South Carolina. For example, recent polls from the South Carolina House Republicans have included samples where seniors make up, in some cases, more than 60 percent of the poll. That is a far higher share of the vote than in the past two primary elections.
In the NBC poll, by contrast, voters 60 years or older make up just 36 percent of the poll sample. That number is more consistent with past voting trends. Given Trump’s strong support among older voters, that small change accounts for much of the difference in the head-to-head numbers.
The same is true for “very conservative” and “evangelical” voters. The NBC sample includes these voters in proportions consistent with past voting. In the NBC poll, evangelicals make up 65 percent of the sample, which was their proportion of the vote in 2008 and 2012. “Very conservative” voters make up 25 percent of the voters in NBC’s poll. That is generally consistent with past elections, although perhaps a little low. In 2012, “very conservative” voters made up 36 percent of the electorate.
Among “very conservative” voters, Ted Cruz leads Trump by 20 points, 42-22. Among evangelicals, Trump leads Cruz by just 3 points, 29-26. The final breakdown of these votes, and how much of the electorate they comprise, will be the deciding factors in the South Carolina results.
Trump’s strongest support is among new voters. Trump leads Cruz among voters who have never participated in a Republican primary by 17 points. Among past primary voters, the race is a jump ball. The NBC poll estimates that around 20 percent of the voters will be new on Saturday. If Trump can turn out new voters, he will have an edge in the final vote.
The NBC poll has a very large sample. It interviewed 1,227 Republicans for its “potential Republican electorate” estimates and 772 “likely” Republican voters. The margins of error are 2.8 percent and 3.6 percent respectively.
According to the NBC poll, there are essentially two different races in South Carolina. Trump and Cruz are locked in a tight battle to win the state. Marco Rubio and Jeb Bush are in a very tight race for third place. Beyond the final standings, however, the vote margin between the candidates will be critical in how the rest of the campaign unfolds.