On July 23, Gravis released the results of a new national poll, in which respondents were asked for whom they would vote if the nominees were Hillary Clinton for the Democrats and Donald Trump for the Republican Party.
Gravis poll results
The results show that 49.0% of interviewees are going to cast a ballot for former First Lady Hillary Clinton, whereas 51.0% are going to vote for billionaire Donald Trump.
The poll was in the field between July 21 and July 22. The sample size was 3462 participants. There is a sampling error of +/-1.7 percentage points. Considering this error margin, the race is currently a statistical tie.
Putting the results in context
As any other method, polls are subject to bias. Thus, as a general rule, don't rely too much on the results of an individual poll. At the very least, one should examine how a poll's results compare to benchmark forecasts.
For the following analysis, we translate Clinton's and Trump's raw poll numbers into shares of the two-party vote. This procedure yields values of 49.0% for Clinton and 51.0% for Trump. In the latest Gravis poll on June 18 Clinton obtained 51.0%, while Trump obtained only 49.0%.
Comparison to other polls
Trump is currently at 48.2% of the major two-party vote according to an average of recent polls. This value is 2.8 percentage points lower than his respective numbers in the Gravis poll. This difference is outside the poll's sampling error, which suggests that the poll is an outlier.
The poll in comparison with PollyVote's prediction
The most recent PollyVote predicts Trump to gain 47.7% of the two-party vote. This means that the PollyVote forecast is 3.3 points below his polling numbers. The PollyVote forecast is therefore outside the poll's margin of error.