Are the exit polls, on which just about every elections analyst has relied, wrong? That’s a question raised by New York Times Upshot writer Nate Cohn — a question whose answers have serious implications for how you look at the 2016 general election.

Standard analysis is that Democrats have a built-in advantage because the electorate is increasingly non-white. The exit polls say the white percentage of the electorate declined from 77 percent in 2004 to 74 percent in 2008 and 72 percent in 2012. In that year, they said, 13 percent of voters were black, 10 percent Hispanics, 3 percent Asian.

Since then, these groups have been voting heavily Democratic, by varying margins, and analysts have argued that it’s very hard for a Republican to win, especially one who has antagonized non-whites, as Donald Trump has.

But exit polls may not be accurate, Cohn argues. As he points out, they are designed not to accurately represent the proportions of each demographic group, but to indicate the actual result, within a statistical margin of error, and to show the differing responses of significant subgroups.

Moreover, as Cohn doesn’t mention, the results are massaged by the exit pollsters and media analysts, who are aware that some voters (the young, for example) are more likely than others to fill out exit poll questionnaires.

So Cohn looks at two other sources of information on how people voted, the Census Bureau’s Current Population Survey and the Democratic firm Catalist’s voter file compiled from public voting records.

Both sources, like exit polls, have their weaknesses. Many non-voters tell the Census Bureau they voted. Voter records are often erroneous or out of date. Even so, the two sources paint a significantly different and possibly more accurate picture of the electorate than the exit poll.

The CPS and Catalist report that the 2012 electorate was 74 and 76 percent white — higher than the exit poll’s 72 percent. They say that only 15 percent of voters were under 30, not 19 percent as in the exit poll, and that 61 and 62 percent were 45 or older, not 54 percent as in the exit poll.

Most significantly, they peg the proportion of non-college-graduate whites over age 45 — Donald Trump’s core group — as 30 and 29 percent of voters, significantly higher than the exit poll’s 23 percent.

Assuming these data are correct, Cohn estimates that 34 percent of Barack Obama’s voters in 2012 were non-college whites, not the 25 percent that the exit poll indicates. Obama’s share of that demographic fell in 2008, but mainly in the South, and held up in most of the North, including target states Ohio, Wisconsin, Iowa and Colorado.

In other words, Democrats are more dependent on non-college whites than most analysts assume. For years they’ve lost ground among this group, but they could lose more, in which case Obama’s 51 percent 2012 majority may not be duplicated.