As we wrote yesterday, Ernie Tedeschi, an economist and former Treasury Department official, took the data from the USC/Los Angeles Times “Daybreak” poll of the election and changed what pollsters call the “weighting.”

Tedeschi’s reweighted version shows Hillary Clinton leading for most of the summer and fall. As of today, his version shows Clinton ahead by 5.3 percentage points, while the official version of the poll shows Donald Trump with a tiny lead — of 0.6 points, basically a tie.

Tedeschi’s work highlights a crucial point about polling: The numbers that polls present almost always involve a series of decisions made by pollsters, and those decisions are always subjective. Pollsters make their best efforts to get the numbers right, but given the same data, different pollsters will often come up with different results.