When Mr. Cantor lost, headlines labeled it an “earthquake” and a “shocker.” And it was, for people who relied solely on polls. It was less so for reporters — like Jake Sherman of Politico, Jenna Portnoy and Robert Costa of The Washington Post and the staff at Breitbart News — who went to Virginia, and talking to actual humans, picked up on the potential trouble for Mr. Cantor.

Of course, the data journalism at FiveThirtyEight, The Upshot at The Times and others like them can guide readers by putting races in perspective and establishing valuable new ways to assess politics. But the lesson in Virginia, as the Washington Post reporter Paul Farhi wrote at the time, was that nothing exceeds the value of shoe-leather reporting, given that politics is an essentially human endeavor and therefore can defy prediction and reason.

After this column was published online last week, some interpreted that as saying “down with data,” as if it were a binary choice between data journalism and traditional reporting. But it is not an either-or proposition. When done right, each can enhance — and, if necessary, serve as a corrective for — the other.

To be fair, given Mr. Trump’s reality television background, there was some cause to suspect that his presidential announcement last summer signaled that his campaign would be part “performance art” and that there was the possibility of a free fall, as McKay Coppins of BuzzFeed wrote.

It was another thing to declare, as The Huffington Post did, that coverage of his campaign could be relegated to the entertainment section (and to add a disclaimer to articles about him) and still another to give Mr. Trump a “2 percent” chance at the nomination despite strong polls in his favor, as FiveThirtyEight did six months before the first votes were cast. Predictions that far out can be viewed as being all in good fun. But in Mr. Trump’s case, they also arguably sapped the journalistic will to scour his record as aggressively as those of his supposedly more serious rivals. In other words, predictions can have consequences.

Yet when things swung around for Mr. Trump, they sometimes went too far the other way, so that as he approached the Iowa caucuses with a head of steam, much of the reporting assumed that Mr. Trump was on the verge of winning there. But once again the more accurate picture emerged from on-the-ground reporting like that of Trip Gabriel of The Times, who found that organizational problems were undercutting Mr. Trump’s polling strength. It seemed prescient when Mr. Trump lost.

The problems weren’t at all only due to the reliance on data. Don’t forget those moments that were supposed to have augured Mr. Trump’s collapse: the certainty that once the race narrowed to two or three candidates, Mr. Trump would be through, and what at one point became the likelihood of a contested convention.