NBC-WSJ-Marist published the results of a new poll. In this poll, interviewees from Ohio were asked for whom they will vote: Donald Trump or Hillary Clinton.
In Ohio, the election outcome is usually close. Therefore, the state is commonly considered a swing state, which makes it particularly interesting from a forecasting perspective.
NBC-WSJ-Marist poll results
According to the results, former New York Senator Hillary Clinton and real estate developer Donald Trump can draw on equal levels of support, each with 39.0% of the vote.
This poll was conducted from July 5 to July 10, among a random sample of 848 registered voters. There is a sampling error of +/-3.4 percentage points. Considering this error margin, the race is currently a statistical tie.
Putting the results in context
Single polls can contain large errors, and should be treated with caution. Rather than trusting the results from single polls, the evidence-based approach is to use combined polls or, even better, a combined forecast that relies on forecasts from different methods, each of which relies on different data.
For the following analysis, we convert the candidates' raw poll numbers into shares of the two-party vote. The results of the actual poll mean 50.0 % for Clinton and 50.0 % for Trump for the two-party vote share.
Results compared to other polls
In comparison to the average results of other polls Clinton performed worse with 0.5 percentage points, while Trump did better with 0.5 percentage points. This margin is outside the poll's sampling error, which means that the poll is an outlier.
Results compared to the combined PollyVote prediction
The most recent PollyVote predicts Clinton to gain 50.7% and Trump 49.3% of the two-party vote in Ohio. Clinton has 0.7 percentage points less and Trump has 0.7 percentage points more when the results of the poll are compared to the combined PollyVote forecast for Ohio. The PollyVote forecast is therefore outside the poll's sampling error.