The political world was shocked Monday morning to see Donald Trump had taken the lead over Hillary Clinton in national polls. In a CNN poll released Monday and conducted Friday through Sunday, Trump leads Clinton by 5 percentage points in a four-way matchup that includes two third party candidates. That’s a 10 point swing in Trump’s favor over Clinton from a CNN poll conducted July 13 through 16.
But here’s why everyone should take this poll and all other polls for the next three weeks with a grain of salt: historically, polling shifts wildly during and immediately after political conventions and then settles down two to three weeks afterward.
In fact, polling shifts so wildly during conventions that it’s actually more accurate to look at polls conducted right before the conventions than polls taken during or right after. According to research conducted by Josh Katz and Kevin Quealy at the New York Times, polls right before conventions are off from the final election result by about 6 percentage points. During convention season, that rises to about 8 percentage points. It won’t be until roughly mid-August or later that polling historically returns to accuracy within 6 percentage points of the final election result.
If you must continue to look at polls, it’s at least better to look at polling averages or election models that should dull some of the noise of polls affected by the convention. For example, the RealClearPolitics polling average shows Trump ahead by 0.2 percentage points in its two-way race average, but down by 0.6 percentage points in a four-way race that includes Gary Johnson and Jill Stein.
The election model at the New York Times gives Clinton a 68 percent chance of winning, though that appears to be down about 5 percentage points from just a few days ago. The FiveThirtyEight election model shows a similar trend, with Clinton’s odds of winning dropping from 63 percent before Trump’s convention to 58 percent on Monday.
Betting markets, on the other hand, haven’t been moved by the conventions. The morning of July 18, Clinton had about 69 percent chance of winning the election. That’s basically true as of Monday at noon, too. Her odds never changed by more than 2 points during the Republican convention.
It’s easy to get caught up in the constant churn of the news cycle and new polls. But for the next few weeks, take a deep breath and remain calm until it’s more reasonable to trust polls again.
Jason Russell is a commentary writer for the Washington Examiner.
