The New York Times/Siena University polls faced an early test during Alaska’s top-four Senate primary held in August. Results showed Democrat Mary Peltola had a six-point lead, which matched the actual outcome closely. Despite this, pollsters still worry about nonresponse bias, where supporters of President Trump might not answer surveys.
Answers to readers' queries about the possible reasons a survey could misfire.
If my inbox is any indication, we've reached the point when everyone just wants to know whether the polls will be right.
Fair enough, so in this newsletter, I'll respond to a few of your questions about the specific risks facing pollsters today.
But first I wanted to report one rare opportunity to put our New York Times/Siena University polls to an early test: Alaska's unusual top-four Senate primary, held in August. It's a plausible test because the primary ballot is a lot like a general election: Everyone was eligible to vote, and candidates from all parties appeared on the same ballot, with the top four vote-getters advancing to the general election.
If the polls were badly off, we might expect to see it by comparing the results of the primary with the polling results among those who participated in the primary.
The results among polling respondents who voted in the primary look pretty good. Among those who voted in the primary, the Democrat Mary Peltola had a six-point lead over the Republican incumbent, Dan Sullivan. That's quite similar to the actual Alaska primary result, when the Democratic candidates outgained the Republicans by five points (or seven points if we exclude the vote for the "other" Dan Sullivan, who clearly won the support of Democratic voters who tried to advance him to play a spoiler role).
So it doesn't seem our Alaska poll overestimated how well the Democrats would do, at least among this segment of the electorate. That's certainly more reassuring than if the poll had found, say, Ms. Peltola ahead by 14 points among primary voters. But it won't let pollsters sleep easy at night either. Pollsters face all kinds of risks, and you asked about many of them:
Nonresponse bias
The most common reason to think polls will overestimate Democrats' strength is nonresponse bias -- the possibility that polls will be biased because President Trump's supporters don't respond to surveys.
Subscribe to The Times to read as many articles as you like.