Attendees hold signs at a Bernie Sanders rally in Michigan last month. Sanders and Donald Trump have run campaigns that seemed paired to the preferences of people who don’t normally vote. Photograph by Sean Proctor / Bloomberg / Getty

American elections are peculiar instruments of democracy, because they are so consistent in whom they leave out. In the past three Presidential elections, about forty-five per cent of those eligible to vote chose not to. And although this fact has been the subject of some public-spirited anxiety, it has generally not troubled political scientists too much, because it seemed as if non-voters had more or less the same view of the parties as voters did. Stretch the electorate to two-thirds of those eligible, or three-quarters, or make voting mandatory, and it has long seemed that the votes would be distributed in roughly equivalent proportions: about half the vote for Democrats, half for Republicans, with some variability reserved for the shape of current events.

But compare voters to non-voters and you get two very different-looking groups. The non-voters are younger, according to a 2014 Pew study. They are also less educated and have lower incomes. On the whole, there are fewer Protestants and more Catholics among non-voters than among voters, as well as fewer whites. Non-voters and voters might have roughly the same view of the Democrats, but you wouldn’t expect them to have the same view of much else.

In 2013, the political scientists Jan Leighley, of American University, and Jonathan Nagler, of New York University, published the results of a study that compared, among other things, the political views of voters and non-voters, dating back to 1972. On most social issues (abortion, L.G.B.T. rights), there was no measurable difference between them. Non-voters were more inclined toward isolationism. (Leighley and Nagler thought this might be because non-voters knew more soldiers than voters, and were more reluctant to see them sent into conflict.) The difference on economic matters was much more dramatic. Non-voters, Leighley and Nagler found, favored much more progressive economic policies than voters did. They preferred higher taxes, and more spending on schools and health care, by margins that hovered around fifteen per cent. “The voters may be representative of the electorate on some issues,” Leighley and Nagler wrote, “but they are not representative of the electorate on issues that go to the core of the role of government in modern democracies.” That non-voters had the same partisan preferences as voters only seemed to strengthen the finding—they wanted more redistribution regardless of whether they were Democrats or Republicans.

As unpredictable as this Presidential campaign has been, its two most successful outsider candidates, Donald Trump and Bernie Sanders, have in this sense followed established patterns: they have run campaigns that seemed perfectly matched to the preferences of people who do not normally vote. Both Sanders and Trump have done little to distinguish themselves from their parties on social issues, but they have moved to their parties’ left on economic matters and suggested that they would be more skeptical of international entanglements. If you were targeting non-voters on the right, you would design a campaign that looked very much like Donald Trump’s. If you were targeting non-voters on the left, you would emphasize almost exactly the same issues as Bernie Sanders.

There is an interesting distinction, the Harvard political scientist Stephen Ansolabehere points out, between the generic non-voter and the “marginal voter”—the next person in. In recent Presidential election seasons, campaigns have shifted from general trawls of non-voters to precise expeditions for small groups of marginal voters, helped along by the new practice of micro-targeting. New voters increasingly do not just accrue but are actively selected by them. Much has been made of the use of micro-targeting by the Ted Cruz campaign, which went so far as to support legalizing fireworks in Iowa in order to pull in a particular group of voters. The Trump and Sanders campaigns have been doing something else entirely. Rather than aiming for the few non-voters most likely to select them, they have aimed for the broader public, relying on rallies and using victory speeches as infomercials, mass appeals that have seemed a little retro.

Perhaps this explains some of the surface similarities of their supporters. Several weeks ago, Henry Brady, the dean of the Goldman School of Public Policy at the University of California, Berkeley, tried to make sense of new data from the American National Election Survey, an academic group that did extensive surveys of voters in the early primary states, along the lines of much more detailed exit polls. Brady grouped each voter’s responses according to the candidate that voter supported, and then plotted the candidates by ideology, from Sanders on the left to Cruz and Trump on the right. The graphs kept resolving into an elegant U-shape: For many questions, the responses of Sanders voters most resembled those of Trump voters. They were the youngest, and the least educated. On certain issues—“xenophobia, racism, nationalism,” Brady said—they occupied opposite extremes. On others, the differences between them were slight. “Trump voters are almost as worried about economic inequality as Sanders voters,” he said, and more worried about it than anyone else.

One story that you could tell about the second half of the Obama Presidency is that the politics of the country have been pushed along by movements—Occupy, Black Lives Matter, the Tea Party—that are not basically about the contest between Democrats and Republicans but, rather, emanate from outside them. The scope of what counts in politics, of whose voices matter, has been broadened beyond those who normally vote. No one knows whether these populist tendencies will abate or change each of the parties, but this year it is clear that the traditional biases of electoral politics have given way to the more various terrain beneath them. The influence advantage that voters have over non-voters is more tenuous; the distance between the concerns of the campaigns and the experience of the country has narrowed. This election season has been strange and often alarming, but that is in part because it has been aimed at a broader audience—because it has been, in some crude ways, more democratic than what came before.