But polls from previous election cycles one year out—that is, from the November before the presidential election—suggest that this picture of a surly, restive electorate may be an illusion. Could it be that the Donald’s numbers don’t really bespeak a radically new Republican temper? Or that Bernie Sanders’s numbers indicate something less than a Democratic lurch leftward? The perceived discontent and restlessness this fall may well be more noise than signal, and not at all unprecedented.

Of course, sometimes the early polls do get it right. Typically this happens in races with few competitors, as when then–Vice President Al Gore led the Democratic field throughout 1999, or in races with an overwhelming favorite, as Ronald Reagan was in 1979. William Mayer, a political scientist at Northeastern University, found that in contested primary races since 1980, front-runners polling at 34 percent or higher in September the year before the election went on to win the nomination six of eight times—but not one of the five front-runners who fell short of that threshold ultimately prevailed.

Looked at over the long run, then, early polls tend to be startlingly unreliable predictors of final outcomes. They capture not the convictions of a newly aroused and assertive body politic, but instead the fleeting impulses of an electorate that remains overwhelmingly disengaged.

The first thing to keep in mind is that a year before the general election, most voters aren’t paying attention yet. Campaign reporters and political junkies—and probably anyone reading this article—are apt to forget this, because we talk about the race incessantly ourselves. But only about 10 to 20 percent of voters are tracking the campaign closely. Normal people tend to tune out the arcane, minute developments that the Twitterati are quick to label game changers. Believe it or not, they have better things to do.

Their indifference may be justified. A California voter with a modest interest in public policy has no good reason to figure out whether she prefers John Kasich or Rand Paul or Carly Fiorina on the Islamic State or abortion or entitlements, because by the time she votes next June, there’s a good chance none of them will be in the race. She will begin studying the candidates carefully only in the days just before her state’s primary.

This inattention means that early poll numbers are based on shallow preferences. “The media don’t always report the numbers that say ‘not sure’ or ‘don’t know enough,’ ” says David Karol, a political scientist who has studied the nomination process. Many people who are actually undecided, he adds, will cough up a name when a poll-taker calls and prompts them. Those responses just don’t tell us much.

What the early numbers do reflect is name recognition. Amid all the explanations for Trump’s summer surge—his bluntness, his immigration message, his political innocence—the most important one may simply be that he’s famous. Everyone knows who he is. In contrast, names like Marco Rubio and Ted Cruz, familiar inside the Beltway, evoke shrugs or blank stares from many people. Name recognition accounts for the misleading early success of many past front-runners. It explains why the 2000 vice-presidential nominee, Joe Lieberman—who was far too conservative to ever win the Democratic primary—was the front-runner for a while in 2003. It even explains, in part, why George W. Bush bolted into first place among Republicans in 1999. Some respondents literally thought the man they were being asked about was the former president. “Despite the Governor’s popularity in the polls,” wrote Richard Berke in The New York Times in 1999, “surveys continue to show that many Republicans confuse Mr. Bush with his father.”(Name recognition also helped Jeb Bush vault to a lead in the polls earlier this year, although his weak campaign-trail performance, and perhaps lingering discontent with his brother’s tenure, led his numbers to fall.)