According to the Latest Poll...
As Election Day nears, it’s one poll after another. But what do they really mean?
As soon as the Republican Convention wrapped up at the end of August, pollsters scrambled to measure its effect on voters.
Rasmussen, one of the major polling firms, released a poll showing 48 percent of voters favoring Mitt Romney, the Republican presidential candidate, and just 44 percent for President Obama, the Democrat.
Good news for Romney, right? Not so fast. A Gallup poll showed Obama leading by one point. A third poll, by Ipsos/ Reuters, showed them in a dead heat at 45 percent each.
So what’s going on? Why are three different polls taken the same week coming up with such different results? The short answer: Polls are complicated.
Politicians use polls to find out what voters think and care about and to tailor their messages to them. The news media use polls to give the public a sense of which candidate is ahead at any given time and why. Polls can have both direct and indirect effects on voters— especially in a tight contest like this year’s race for the White House.
“They can stimulate people to give money or to volunteer for a campaign,” says Michael Traugott, a polling expert at the University of Michigan. “They can make people think that their vote is worth more if the margin is close, meaning they have an impact on turnout.”
It’s just as important, however, to know the limits of any individual poll.
First, a poll tells us about the present, not the future: It’s not a crystal ball, but a snapshot of public sentiment at a particular moment—and not a perfectly sharp snapshot.
The basic premise behind polling is that by questioning a surprisingly small number of people, you can get a good sense of what an entire city or state or country is thinking.
Most reputable political polling relies on a method called “probability sampling”: If you select people at random from a population, you have a good chance of reflecting, within a few percentage points, the opinions of everyone.
But there are many possible sources of distortion. How questions are worded—and even the order in which they’re asked—can sway the results.
And then there’s the electorate itself, which isn’t always easy to pin down. Although a large portion of the American public is committed to one party or the other, there’s always a segment that wavers, or stays undecided (or uninterested) until late in a campaign. Those swing voters often determine who wins, and their views can keep changing up to the very last minute.
One of the most embarrassing errors in polling history occurred during the 1948 presidential race, when all the major polling organizations declared that Thomas E. Dewey, the Republican, would defeat the Democrat, President Harry S. Truman. Dewey’s lead seemed so insurmountable that they’d stopped polling several weeks before the election and missed a late swing toward Truman.
Even on election night, experts and the media were convinced Dewey would win. More than 60 years later, the photograph of a jubilant Truman holding up a copy of the Chicago Daily Tribune declaring “Dewey Defeats Truman” remains a warning against relying too heavily on polls.
Today, surveys are conducted right up to Election Day—and at polling places for “exit polls” in which voters are interviewed just after voting.
But even exit polls are fallible. In Florida, in the 2000 presidential race, a combination of bad polling data in a handful of precincts and mistakes in actual vote counts led most TV networks to call a race—between Republican George W. Bush or Democrat Al Gore—which was in fact too close to call. Because the electoral vote was so tight, it all came down to a couple hundred votes in Florida. It took four weeks of recounts and lawsuits and the Supreme Court to sort out Florida and decide the election for Bush.
THE CELLPHONE CHALLENGE
Pollsters have always had to adapt to changes in technology. When scientific surveys began in the mid-1930s, most polling was done face-to-face. It wasn’t until the late 1970s that most polling companies switched to phones.
Today, cellphones are presenting an enormous challenge. In 2008, most pollsters still called landlines only; now most include cellphones as well. But there’s no standard yet for what percentage of respondents must be cellphone-only households.
About 30 percent of the U.S. population use cellphones only. This group tends to be younger, more urban, and more likely to be black or Hispanic—all groups that lean Democratic. So the wrong mix of landlines and cellphones can skew a poll’s results.
Another big issue for pollsters is the rising number of people who refuse to respond to surveys or can’t be reached: How do they differ from the people who will answer the phone and take the 15 or 20 minutes that most surveys require?
“Fewer and fewer people are willing to talk to us,” says pollster Mark Mellman. “So far... the polls have stayed reasonably accurate. But at some point, that could change.”
Despite these cautions, properly conducted polls are still the best way to find out what people are thinking at any given moment, and in a democracy, that’s important to know. So be skeptical when candidates say the only poll that counts is on Election Day. Often they’re the ones who think they’re behind.