## DataLab

On Thursday night, the University of New Hampshire (UNH) published its latest Granite State Poll. The survey showed Republican Scott Brown down just 2 percentage points to incumbent Democratic Sen. Jeanne Shaheen (46 to 44 percent). Brown was behind by 12 points in the UNH poll a month ago. It’s a big shift in a Senate race that FiveThirtyEight believes Shaheen is a 90 percent favorite to win.

Indeed, a number of news organizations jumped on the poll as a sign that Brown is “closing the gap” with Shaheen.

I only have one question: Have we learned nothing?

Take the average, people. In the final week of the 2012 presidential campaign, there were multiple polls showing Republican Mitt Romney winning in Iowa. In October 2012, there was a poll showing Obama winning Arizona. Neither happened. Even good pollsters will occasionally have a result that is an outlier, and with enough polling, you’re guaranteed to have outliers.

Don’t make too much of any single poll. Focus on the average.

It’s possible that Brown is slicing into Shaheen’s lead, but there hasn’t been any sign from any other pollster that Shaheen’s edge is down to 2 percentage points. The other three surveys in the race taken after July 1 gave Shaheen an advantage of 5, 8 and 10 points. Before Thursday, no pollster over the past six months has given Shaheen anything less than a 3-point lead.

Moreover, it’s not like we haven’t been through this song and dance with UNH before. In 2012, the presidential campaign was as stable as perhaps any campaign in modern history. Even when the national polls moved around a lot, swing-state polling was fairly consistent in showing a small but clear Obama edge.

Yet, as many have pointed out online, the UNH poll was not part of this group. In late September, the Granite State Poll gave Obama a 15 percentage-point blowout win in New Hampshire. Next week, that lead was down to 6 points. Two weeks later, it was up to 9. Two weeks later, it was even. Two days later, the lead was back up, to 4 points. In the same span, the Huffington Post Pollster aggregate of polls never had Obama’s New Hampshire lead rising above 5 percentage points or dropping below 2 points.

I point out past polling in the Brown vs. Shaheen race and UNH’s polling history not to say that UNH is definitely wrong in finding that Brown is in a near tie with Shaheen. It’s just that we should be suspicious when a poll seems like an outlier, especially when the particular pollster has had bouncy results in previous elections. We should wait for more polling before revising our assessment that Shaheen is in strong shape for re-election.

Harry Enten is a senior political writer and analyst for FiveThirtyEight.

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