Excellent analysis by Nate Cohn of the New York Times “Upshot” in interpreting the methods and merits of the USC Dornsife/Los Angeles Times Daybreak poll, which has baffled both sides of the aisle in 2016, zigging while everyone else zagged. The survey has consistently shown Donald Trump outperforming all other available numbers. Is the poll purposely biased, somehow better than all the rest or just flawed?

The first two are improbable, while the latter seems likely. As Cohn notes, USC/LAT is “admirably transparent,” which allowed him to discern the two key problems with the system: 1)  It weights for very tiny groups, which results in big weights, and 2) It weights by past vote. Number two is a particularly unorthodox practice.

The opening:

There is a 19-year-old black man in Illinois who has no idea of the role he is playing in this election.

He is sure he is going to vote for Donald J. Trump.

And he has been held up as proof by conservatives — including outlets like Breitbart News and The New York Post — that Mr. Trump is excelling among black voters. He has even played a modest role in shifting entire polling aggregates, like the Real Clear Politics average, toward Mr. Trump.

How? He’s a panelist on the U.S.C. Dornsife/Los Angeles Times Daybreak poll, which has emerged as the biggest polling outlier of the presidential campaign. Despite falling behind by double digits in some national surveys, Mr. Trump has generally led in the U.S.C./LAT poll. He held the lead for a full month until Wednesday, when Hillary Clinton took a nominal lead.

Our Trump-supporting friend in Illinois is a surprisingly big part of the reason. In some polls, he’s weighted as much as 30 times more than the average respondent, and as much as 300 times more than the least-weighted respondent.•