WBUR/MassINC published the results of a new poll on October 12. In this poll, respondents from New Hampshire were asked for whom they will vote: Republican nominee Donald Trump or Democrat nominee Hillary Clinton.
In New Hampshire, the popular vote is often close. Therefore, the state is commonly considered a purple state, which makes it particularly interesting from a forecasting perspective.
WBUR/MassINC poll results
According to the results, 46.0% of respondents indicated to vote for former Secretary of State Hillary Clinton, whereas 41.0% plan to vote for billionaire Donald Trump.
The poll was in the field between October 10 and October 12. The sample size was 501 likely voters. The margin of error is +/-4.4 points. This means that the poll results for the candidates of both parties do not differ significantly.
Putting the results in context
As a general rule, however, you should not have too much faith in the results of single polls, as they can incorporate large errors. Rather than trusting the results from single polls, research in forecasting recommends to consult combined polls or, even better, a combined forecast that draws upon different methods and data.
For the following analysis, we convert Clinton's and Trump's raw poll numbers into shares of the two-party vote. The resulting figures are 52.9% for Clinton and 47.1% for Trump. For comparison: 55.3% was obtained by Clinton in the WBUR/MassINC poll on September 29, for Trump this result was only 44.7%.
Comparison to other polls
An average of recent polls in New Hampshire sees Clinton at 52.5% of the two-party vote. Relative to her numbers in the WBUR/MassINC poll Clinton's poll average is 0.4 percentage points worse. This difference is within the poll's margin of error, which suggests that the poll is not an outlier.
The poll in comparison with PollyVote's prediction
The current PollyVote forecasts Clinton to gain 52.7% of the two-party vote in New Hampshire. That is, the PollyVote forecast is 0.2 points below her polling numbers. Again, a look at the poll's error margin indicates that this difference is insignificant.