New York Times: “A number of things can affect a poll’s results, including the wording of a horse-race question and the order that items are asked. In CNN and Fox News polls this year, respondents have typically been asked for their opinions on each of the Democratic presidential candidates, among other questions, before being queried about their vote preference.”

“In Quinnipiac’s polls — as well as those conducted by Monmouth University, which have also shown Ms. Warren climbing steadily — people have not typically been asked to evaluate the candidates one-by-one before giving their vote choice.”

“If such small differences in survey structure are indeed having an effect on results, it may reflect the fact that many respondents are not yet certain about their feelings.”

Matthew Yglesias: “Democratic voters are stuck in a self-destructive loop.”

“The loop begins and ends with polls. Pollsters know that Democrats want to know who is the strongest candidate against President Donald Trump, so they conduct a lot of head-to-head polls matching Trump up against various contenders. The polls show that the best-known Democrats — former Vice President Joe Biden, Sen. Bernie Sanders, and Sen. Elizabeth Warren — are the strongest candidates against him, which likely boosts them in the polls. This makes it hard for the lesser-known candidates to get attention, which further ensures they’ll do poorly in the head-to-head polls against Trump.”

“The problem is that head-to-head polls at this stage in the race overwhelmingly reflect the challenger’s name recognition rather than anything that would help you predict an election outcome that’s more than a year in the future.”

Aaron Blake: “The divergence in Iowa polls highlights a challenge for observers early in the 2020 election: While we have an abundance of national polls, early-state polls have been few and far between, and that makes it incredibly difficult to draw conclusions about whose organization and message are appealing to the voters who matter most. It’s not clear yet whether we have a true and accurate picture of the race, even as it stands now.”

“The pace of early 2020 polls is significantly slower in Iowa and in New Hampshire than it was four years ago. The poll Wednesday was just the second live-caller poll released in Iowa since the beginning of August, compared with six over the same period in 2015. In New Hampshire, there have been just two over the same span in 2019, compared with four in 2015.”

“If you expand the universe to all quality polls and stretch it further back in the race, the pattern holds. There have been just seven quality polls, including automated and online surveys, in Iowa since the start of May, compared with 14 over the same period in 2015.”

David Byler: “But we’re not completely in the dark about who is going to be the Democratic nominee. National primary polls taken at this point in the process don’t have a great track record of picking the eventual winner. But one of the candidates in the top three or four in the national polls often does become the nominee. And while true polling longshots — those polling at zero percent or close to it — do still have some chance of winning, the historical record doesn’t provide much reason for optimism.”

Perry Bacon: “In the runup to the 2016 presidential election, this same question came up, and FiveThirtyEight analyzed general election polls from 1944 to 2012 that tested the eventual nominees and were conducted in the last two months of the year before the election (so for 2012, that would be November and December of 2011). On average, these polls missed the final result by 11 percentage points.”

“The last presidential election featured one of the more accurate sets of early polls for this point in the cycle: Hillary Clinton led Donald Trump 46.2 percent to 41.2 percent in an average of all polls conducted in November and December 2015, missing the eventual national popular vote margin by about 3 points. (The actual result was Clinton 48.0 percent, Trump 46.0 percent.)”

Nathaniel Rakich: “There are already a lot of things that a smart poll-watcher has to account for when comparing surveys. Were they done by the same pollster? Did they query the same type of population (likely voters, registered voters, all adults)? To this list, the volatile 2020 Democratic primary field has added one more: Do they ask about the same candidates?”

“With upwards of 20 candidates and potential candidates, pollsters are forced to make editorial decisions about whom to ask about. And with new candidates still popping up out of nowhere, the field is enough in flux that it looks different every month.”

Politico: “The logjam of nearly two dozen declared or likely Democratic presidential candidates is overwhelming public pollsters trying to measure the 2020 primary. New surveys are cramming up to 23 Democrats into their questionnaires after the [DNC] set a low, 1 percent polling threshold to gain admittance into the party’s first primary debates.”

“The miles-long list of candidates has created an unusual set of methodological challenges for pollsters already battling declining engagement with their surveys. But pollsters say the criteria also put them in a no-win situation: A pollster’s decision about whether to include a candidate or not could be a make-or-break choice for that campaign, especially the lesser-known and first-time White House hopefuls hoping to make the debate stage.”