To most, Joe Biden’s clear lead in latest state polls means that he has the early edge within the race for the presidency. To others, it’s not so s
To most, Joe Biden’s clear lead in latest state polls means that he has the early edge within the race for the presidency. To others, it’s not so significant. In any case, Hillary Clinton additionally held a transparent lead within the state polls, and but Donald J. Trump gained the election.
4 years later, it’s honest to wonder if there’s a severe threat of one other systematic polling error. The reply isn’t minimize and dried.
There’s all the time an opportunity of a scientific polling error, even when the explanations aren’t evident prematurely. This time, there are apparent causes for concern. Many state polls endure from the identical methodological points that had been partly and even largely accountable for the miss 4 years in the past, regardless of many alternatives to enhance. But on the identical time, lots of the main causes of error in 2016 appear considerably much less acute.
What’s higher than in 2016: undecided voters
One main supply of the 2016 polling error is far much less of an element than it was 4 years in the past: voters who’re undecided or say they may vote for a minor-party candidate. These voters appeared to interrupt overwhelmingly towards Mr. Trump, particularly within the comparatively white, working-class battleground states.
This time, far fewer voters are telling pollsters they’re undecided, and meaning much less room for a late shift amongst these voters to trigger a polling error. At this level in 2016, about 20 % of voters both supported a minor-party candidate or stated they had been undecided. At this time, the quantity is about half that degree.
What’s a little bit higher than in 2016: schooling weighting
One other supply of polling error was the failure of many state pollsters to regulate their samples to adequately symbolize voters with out a faculty diploma. Voters with a school diploma are far likelier to answer phone surveys than voters with out one, and in 2016 the latter group was far likelier to help Mr. Trump. Over all, weighting by schooling shifted the everyday nationwide ballot by round 4 share factors towards Mr. Trump, serving to clarify why the nationwide polls fared higher than state polls.
4 years later, weighting by schooling stays simply as necessary. The hole within the choice of white voters with or with out a faculty diploma is actually unchanged, regardless of the attraction Mr. Biden was speculated to have with much less educated white voters.
In The New York Occasions/Siena Faculty surveys conducted in October, Mr. Biden’s combined lead over Mr. Trump in the core six battleground states — Wisconsin, Pennsylvania, Michigan, Arizona, Florida and North Carolina — was two percentage points. That lead would have been six percentage points had it not been weighted by education or turnout (which correlates with education).
More pollsters are weighting by education today than four years ago. It could still be better, but over all, 46 percent of the more than 30 pollsters who have released a state survey since March 1 appeared to weight by self-reported education, up from around 20 percent of battleground state pollsters in 2016.
Some of the increase is because a handful of pollsters have decided to start weighting by education, a prominent example being the Monmouth University poll. But more of the change is because of the high volume of state online polls, which have always been likelier than state telephone surveys to weight by education.
What could be worse than in 2016: new online polls
There has been an explosion of new online-only state polls. Over the last month, there have been 13 such surveys, representing nearly half of the pollsters who have conducted state polls over this period. In contrast, only 10 online-only pollsters conducted surveys over the final three weeks of the 2018 election, which was about 10 percent of all of the pollsters who conducted surveys in that period.
Online polling isn’t necessarily bad. Many are sophisticated and comparable in quality to a typical live-interview telephone survey. But most of these new state polls take a simple approach: Contact the members of a large online panel, then weight those respondents by standard census demographics and maybe recalled vote choice in 2016 (more on that later). This is inexpensive and easy, but most pollsters have concluded that it’s not great. The panels just aren’t sufficiently representative, especially in small states, to expect a simple methodology to yield a high-quality result.
Until recently, few pollsters have tried to use this approach in state polling (Morning Consult is the most prolific example of a pollster that has done it nationally). But the early evidence suggests that these kind of state polls might lean to the left.
Perhaps the best early data is the AP/NORC/VoteCast polling ahead of the midterms, which combined a traditional telephone survey of 40,000 respondents with a large nonprobability online sample of 110,000 respondents. The online-only element of the survey was fairly comparable to most of the online surveys released in recent weeks, and it wouldn’t have fared well without calibration using the live-interview surveys. It would have overestimated the Democratic result by an average of about five percentage points across 71 races.
Similarly, the new online polls tend to lean to the left of the state telephone polls so far this cycle. In polls conducted since March 15, Mr. Biden has run 6.6 percentage points ahead of Mrs. Clinton’s margin in online state polls, compared with a gain of 3.7 points in live-interview telephone surveys. Notably, the latter figure comes very close to Mr. Biden’s gain in national polls — about four points — over the same period.
Over the long run, these polls might make up a smaller share of the battleground polling than they have so far. But it seems inevitable that new online polls will represent a larger share of state polls this cycle, and so far the best indications are that they’ll lean to the left.
What could be worse than in 2016: recalled vote weighting
More and more, pollsters with fairly mediocre sampling methods are relying on a new tool to bring their results closer to reality: recalled 2016 vote. Here, the pollster asks respondents whether they voted for Mrs. Clinton or Mr. Trump, then adjusts the sample so that the recalled vote choice matches the actual result of the 2016 election.
Weighting on recalled vote choice certainly has its advantages. You could probably hammer even the worst survey into the ballpark. You could probably get a plausible poll result for Wyoming using a sample of New Yorkers this way.
But although this is a surefire way to reduce error, it is very hard to execute without risking a modest systematic bias. And here again, the bias would tend to be toward the Democrats.
There’s a large body of evidence suggesting that people are likelier to recall voting for the winner and less likely to recall voting for the loser. If so, polls weighting on recalled past vote would tend to be biased toward the party that lost the prior election.
It seems that this effect is, at the very least, substantially diminished compared with a decade ago. Even so, it might still be there. In the Times/Siena polls from October, for instance, 6 percent of 2016 voters refused to say whether they backed Mrs. Clinton or Mr. Trump. Those voters backed Mr. Biden by a two-to-one margin, suggesting that they were probably likelier to have supported Mrs. Clinton.
Another issue is that today’s registered voters aren’t exactly the same as those of four years ago: In the interim some people have either died, reached voting age, or moved elsewhere. So it is not appropriate to assume that people who voted in 2016, and are now registered to vote, backed Mr. Trump or Mrs. Clinton by the same margin as in the 2016 result.
It is hard to say whether this is generalizable, but over all 13 percent of the voters who took the Times/Siena polls in 2016 are no longer on their state voter file, and those voters backed Mrs. Clinton by a six-point margin, compared with a one-point lead for Mr. Trump among those who remain registered in the state. Here again, recalled vote weighting might bias a poll by only one percentage point in Mr. Biden’s favor, but the risks start to add up.