Barack Obama’s two victories created the impression of a strong wind at the back of the Democratic Party. Its constituencies — the young, the nonwhite, the college educated — were not only growing but were also voting in increasing numbers. The age-old issue of voter turnout finally seemed to be helping the political left.

The longer view is starting to look quite different, however. None of the other three most recent Democratic presidential nominees — Hillary Clinton, John Kerry and Al Gore — inspired great turnout. George W. Bush, as you may recall, was widely considered to have won the political ground game. In off-year elections, Democratic turnout is even spottier, which helps explain the Republican dominance of Congress, governor’s mansions and state legislatures.

Since Donald Trump’s shocking victory, much of the political diagnosis has focused on white working-class swing voters, and for good reason. Across the industrial Midwest, white voters who had supported Obama and previous Democrats abandoned the party for Trump.

The role that turnout played has been harder to figure out. In the initial days after the election, some people focused on the total number of votes cast, which appeared much lower than four years ago. That impression was wrong, though, because a few million absentee and mail ballots had not yet been counted out West. In the end, overall turnout in 2016 won’t have changed much from 2012.