Quinnipiac published the results of a new poll. In this poll, respondents from Iowa were asked for whom they will vote: Republican Donald Trump or Democrat Hillary Clinton.
In Iowa, the election outcome is usually decided by a narrow margin. This is why the state is commonly referred to as a swing state, which makes it particularly interesting from a forecasting perspective.
Quinnipiac poll results
Of those who answered the question, 44.0% said that they intend to vote for former Secretary of State Hillary Clinton, whereas 50.0% declared that they would give their vote to billionaire Donald Trump.
The poll was conducted from September 13 to September 21. A total of 612 likely voters responded. The sampling error is +/-4.0 points. This means that the poll results for Trump and Clinton do not differ significantly.
Putting the results in context
Individual polls can contain substantial errors, which is why they should be treated with caution. Rather than relying on results from single polls, the best practice is to use combined polls or, even better, a combined forecast that includes forecasts from different methods, each of which includes different data.
For the following comparison, we translate Trump's and Clinton's raw poll numbers into shares of the two-party vote. The resulting figures are 46.8% for Clinton and 53.2% for Trump.
Results vs. other polls
An average of recent polls in Iowa sees Trump at 52.7% of the two-party vote. Relative to his numbers in the Quinnipiac poll Trump's poll average is 0.5 percentage points worse. This margin is within the poll's sampling error, which means that the poll is not an outlier.
Results compared to the combined PollyVote prediction
The current PollyVote foresees Trump to gain 49.4% of the two-party vote in Iowa. This means that Polly's prediction is 3.8 points below his polling numbers. Again, a look at the poll's margin of error reveals that this deviation is negligible.