Among the many polls released yesterday there was one “shock poll” that got more attention than the rest. An NBC News/Wall Street Journal poll released yesterday had Ted Cruz leading Donald Trump among the national electorate of Republican primary voters. Though the poll only had Cruz ahead by 2 percent, 28 percent to Trump’s 26 percent, it was still “newsworthy” in that it was the first to have anyone but Trump leading nationally over the last few months. The NBC News/Wall Street Journal poll directly contradicted two other polls released this week from Quinnipiac and USA Today/Suffolk that had Trump maintaining a large lead nationally over the rest of the GOP field.
Twitter went crazy over the NBC News/Wall Street Journal poll, and it was immediately hyped by the Cruz campaign as a sign that Trump is in decline and Cruz is taking over the lead. Analysts immediately began to question whether the poll was an “outlier” or sign of a real change in the direction of the race.
The NBC News/Wall Street Journal poll has a fairly small sample size of 400 likely voters. That sample gives it a margin of error of +/-4.9 percentage points which means that by the pollsters own admission Trump may actually be at 31 percent support and Cruz may actually be 23 percent if Trump is given the benefit of the margin of error. On the positive side, the NBC News/Wall Street Journal poll is more recent than the other polls, as the sample was taken from February 14, 2016 to February 16, 2016. All other polls that were released over the last week include at least some sampling from February 12 or earlier.
One of the ways to look at the legitimacy of any poll is to compare it to others. Using this measurement the NBC News/Wall Street Journal poll does not match up well.
There have been three other polls released over the last week.
A USA Today/Suffolk University poll released on Monday has Trump with 35 percent support, compared to 20 percent for Cruz, 17 percent for Rubio, and 7 percent for John Kasich. That poll was taken from February 2, 2016 to February 15, 2016. The sample for that poll is small (358 likely voters) giving it a large margin of error.
A Quinnipiac University poll released on Monday has Trump as the leader at 39 percent and Marco Rubio in second at 19 percent. Ted Cruz places third in that poll at 18 percent and John Kasich fourth at 6 percent. That poll has a larger sample size of 602 likely voters giving it a smaller margin of error than the NBC News/Wall Street Journal poll. On the downside for that poll, the survey was taken from February 10, 2016 to February 15, 2016, which means its results are not as recent as the NBC News/Wall Street Journal poll.
Finally, today CBS News released a poll which has Trump leading with 35 percent support. In second is Ted Cruz with 18 percent, followed by Marco Rubio at 12 percent and John Kasich at 11 percent. That poll also has a larger sample than the NBC News/Wall Street Journal poll (581 likely voters). The survey for the CBS News poll was taken from February 12, 2016 to February 16, 2016.
Taken together, the three other recent polls, when averaged together, have Trump at 36.3 percent, Cruz at 18.7 percent, Rubio at 16 percent, and Kasich at 8 percent. The NBC News/Wall Street Journal poll strays from this average by -9 points for Trump, +9 points for Cruz, +1 point for Rubio, and +3 points for Kasich.
So looking at the whole picture, the NBC News/Wall Street Journal poll has a small sample size and it does not compare well to other reputable polls from approximately the same time period.
Of course, it is possible that the NBC News/Wall Street Journal poll does signal a trend, as it is the most recent sample of all the national polls that have been released. However, it is hard to see the race shifting this quickly nationally. The CBS News poll released today is perhaps the best evidence that the NBC News/Wall Street Journal is more of an outlier than a true change in direction in the race. If the NBC News/Wall Street Journal poll was accurate one would expect to see some shift of direction int he CBS News poll, but the CBS News poll remains relatively unchanged compared to the last poll CBS News released in January.
The best test of the NBC News/Wall Street Journal poll will be time. In the coming weeks we will see if Trump is still the leader as a number of states hold their primaries on Super Tuesday.