Results of a new poll carried out by NBC-WSJ-Marist were published on July 16. The poll asked respondents from Florida for whom they would vote if the Democrats nominated Hillary Clinton and the GOP nominated Donald Trump.
Historically, Florida has been a swing state, in which neither the GOP nor the Democrats have had overwhelming support to clinch its electoral college votes. This is why predictions in this state are of particular interest.
NBC-WSJ-Marist poll results
Of those who replied, 44.0% said that they plan to vote for former Secretary of State Hillary Clinton, while 37.0% declared that they would give their vote to billionaire Donald Trump.
The poll was conducted from July 5 to July 11. A total of 871 registered voters responded. The sampling error is +/-3.3 percentage points. This means that the poll results for the candidates of both parties differ significantly.
Putting the results in context
In general, however, don't have too much faith in the results of single polls, as they may incorporate large errors. Rather, one should check how a poll's results compare to benchmark forecasts.
For the following analysis, we translate the candidates' raw poll numbers into shares of the two-party vote. The corresponding figures are 54.3% for Clinton and 45.7% for Trump. On April 27 Clinton obtained 54.4% in the NBC-WSJ-Marist poll and Trump obtained only 45.6%.
Comparison to other polls
An average of recent polls in Florida sees Clinton at 50.3% of the two-party vote. In comparison to her numbers in the NBC-WSJ-Marist poll Clinton's poll average is 4.0 percentage points worse. This difference is outside the poll's sampling error, which means that the poll is an outlier.
The poll compared with PollyVote's prediction
The current PollyVote expects Clinton to gain 49.8% of the two-party vote in Florida. That is, Polly's combined forecast is 4.5 points below her polling numbers. Again, a look at the poll's sampling error suggests that this deviation is significant.