Vox: “The polls were quite close in their forecast for Clinton’s support. Clinton was expected to get 47 percent of the vote; she’s got 47.7 percent so far. On average, the polls understated her state-level support by about a percentage point.”

“Trump, however, was expected to get 44 percent of the vote, and he now has 47.5 percent; the polls undershot his support considerably… As the undecided made up their minds, and as third-party supporters moved toward the major party candidates (as they tend to do in a campaign’s final days), it looks like Trump picked up almost all of them.”

NBC News: “The polls were wrong — all of them. So were the experts, the political consultants and the seasoned officials in both parties who predicted Donald Trump would lead his party to ruin. So were the markets, which had anticipated a Hillary Clinton victory and crashed overnight as her electoral firewall caught ablaze. So was every living president and past presidential nominee of both parties, save Bob Dole, all of whom opposed Trump. So was this reporter and so many like him — and Trump told me as much.”

“Even the GOP polling numbers and analytics we were privy to didn’t show Trump winning. The biggest mistake we made was viewing what seemed to be a very stable race in the polls (with Clinton holding a durable lead), but what ultimately turned into anything but.”

Jake Tapper, on CNN:  “It’s going to put the polling industry out of business. It’s going to put the voter projection industry out of business.”

Our intense focus on election forecasting models over the last few months seems entirely misplaced when this can happen in a single night.

Nate Silver: “Seven of the 19 polls have Clinton leading by 4 points; another four have her ahead by 3 points… It’s worth raising an eyebrow, though, when the polls (other than the L.A. Times) show a range this tight at the end of an election, especially given that they’d diverged so much earlier in the campaign. That probably reflects some degree of herding — for instance, because pollsters stick surveys that seem to be outliers in a file drawer rather than publishing them. So the tight range of polls shouldn’t be taken to mean that everyone’s figured exactly how to poll this challenging election just in the nick of time.”

“Still, the polls clearly agree that Clinton is the favorite, and perhaps has a slight wind at her back for Election Day.”

Huffington Post: “The short version is that Nate is changing the results of polls to fit where he thinks the polls truly are, rather than simply entering the poll numbers into his model and crunching them.”

“Silver calls this unskewing a ‘trend line adjustment.’ He compares a poll to previous polls conducted by the same polling firm, makes a series of assumptions, runs a regression analysis, and gets a new poll number. That’s the number he sticks in his model ― not the original number.”

“He may end up being right, but he’s just guessing. A ‘trend line adjustment’ is merely political punditry dressed up as sophisticated mathematical modeling.”

“One reason there’s so much uncertainty in the race so close to Election Day is the sharp decline in high-quality polls this year,” Politico reports.

“FiveThirtyEight’s Nate Silver calculated the number of polls in competitive states released from Thursday evening through the day on Friday. In all, Silver counted 67 polls across 17 states.”

“That seems like a robust number, but of the 67 polls, only 5 were conducted by live telephone interviewers randomly calling voters on landlines and cell phones — still considered by many to be the most reliable form of polling.”

Harry Enten: “Even at the end of a presidential campaign, polls don’t perfectly predict the final margin in the election. Sometimes the final polls are quite accurate. An average of national polls in the week before the 2008 election had Barack Obama winning by 7.6 percentage points. He won by 7.3 points. Sometimes, however, the polls miss by more. Four years ago, an average of survey results the week before the election had Obama winning by 1.2 percentage points. He actually beat Mitt Romney by 3.9 points.”

“If that 2.7-point error doesn’t sound like very much to you, well, it’s very close to what Donald Trump needs to overtake Hillary Clinton in the popular vote. She leads by 3.3 points in our polls-only forecast.”

Hillary Clinton’s campaign described the ABC News-Washington Post tracking poll that showed Donald Trump ahead as “bad polling,” according to Politico.

Said a senior Clinton aide: “Sorry. It’s just not what we see at all; it’s not what other people seem to have. There just seems to be something about that model that seems off.”

The YouGov Election Model allows you segment voters by demographics, such as age, gender, race and education.

Nate Cohn: “We decided to share our raw data with four well-respected pollsters and asked them to estimate the result of the poll themselves.”

Stuart Rothenberg: “On Election Day 2012, the RealClearPolitics polling average found incumbent President Obama “leading” Republican Mitt Romney by seven-tenths of a point – a statistical dead heat. The actual final result, an Obama victory of 3.9 points, was very different.”

“I cite these numbers not to challenge the RCP average or disparage the pollsters who got the race wrong… Still, the 2012 ‘miss’ should remind us that polling isn’t perfect and even ‘averaging,’ a reasonable strategy, can mislead. Averaging may smooth outliers, but what if one poll always seems to be an outlier, like the Los Angeles Times/USC tracking poll?”

Politico: “While volatility at this stage of the campaign isn’t unexpected, the latest polling data point to an stunningly unstable election environment, unlike any in recent decades.”

Said pollster Neil Newhouse: “There’s every reason to believe that there is huge instability in the current electorate. Four years ago, there were probably 6, 7, 8 percent of voters up for grabs. Now you have 17, 18 percent up for grabs.”

Harry Enten: “It’s easy to find fault with a poll, even from the best pollsters. Anyone passionately arguing that a poll is wrong because its sample has ‘too many [xx]’ or ‘too many of this group are voting for [xx]’ is probably wrong. As you dig into a survey’s crosstabs — looking at college-educated white men, for example, or Hispanics 65 years or older — you’re sacrificing sample size for specificity. The margins of error of subsamples can get huge. Further, most pollsters weight their results by demographics (such as age and race) and not attitudes (like party identification). They do so because historically this has produced the most accurate result. Picking apart individual polls is usually a bad use of time, and the people doing it tend to have a motive.”