Mark Mellman is president of The Mellman Group, a polling and consulting firm.
National polls certainly picked the right winner. Every poll released in the month before the election found Biden leading — and he easily won the popular vote.
Leaving aside Maine, which obviously suffered from unique problems, Senate surveys accurately pegged the vote for Democrats, but consistently underestimated support for Republicans.
On average, public Senate polls came within a point of the vote for Democratic candidates but missed support for Republicans by almost four times as much and, again, in every case understated GOP support.
Decades ago, pollsters’ inside secret of was that undecideds broke overwhelmingly to the challenger.
One of my first races pitted an unknown against a House incumbent in Connecticut. Six weeks out, we were behind by 48 percent to 25 percent. I cautioned the candidate to ignore the margin, noting that most of those undecideds would come our way. And in the end, we won.
Human brains and eyes naturally gravitate to margins — because margins quickly summarize the data. But like all summaries, they can obscure, or ignore, important information.
There’s a difference between a contest where a candidate leads 53 percent to 45 percent, with 2 percent undecided, and one where the lead is 46 percent to 38 percent with 16 percent undecided. The eight-point margin is the same, but the contours of the race, and the outcomes, could well be quite different.