Donald Trump’s Big Bet on Less Educated Whites

A potential victory for Donald J. Trump may hinge on one important (and large) group of Americans: whites who did not attend college.

Polls have shown a deep division between whites of different education levels and economic circumstances. A lot rides on how large these groups will be on Election Day: All pollsters have their own assessment of who will show up, and their predictions rely on these evaluations.

Here’s what the American voting-age population looked like in 2012.

The largest bloc is whites who have no college degree, and the voting-age population of this group is as large as that of voting-age blacks, Hispanics and Asian-Americans combined. Mitt Romney won this group over Barack Obama by 26 percentage points, and Ronald Reagan by 31 points in 1984. But Bill Clinton won this bloc of voters both times he ran. In this year’s political polls, this group favors Mr. Trump by large margins over Hillary Clinton.

However, the voting electorate — the people who actually go to the polls — could look substantially different from the voting-age population. Here’s how the population of actual voters broke down in the last presidential election. Only about half of whites with no college degree voted, leaving about 29 million votes on the table in an election decided by five million votes.

This population is the heart of red-state America. It dominates the rural landscape of swing states like Ohio, Pennsylvania, Iowa and Wisconsin. But it is outnumbered in urban centers and in most suburban areas. A big unknown in this election is how many additional voters will turn out in these counties. On election night, watch for the votes from these areas:

Mr. Trump has argued that his candidacy has generated unprecedented enthusiasm in this part of the electorate. The unpredicted turnout of such a voting group was crucial to Britain’s vote to depart from the European Union.

Mr. Trump’s pursuit of the group has been pointed, but its voting strength has steadily and rapidly declined. Has he stoked enough fervor to make it work?