An important corrective to this assertion of mine: Not turnout, not racism, it was about 20 percent of the white working class who voted for Obama switching to Trump. When I said a "lack of enthusiasm" I meant that they didn't vote - not that they voted instead for Trump.
If turnout played only a modest role in Mr. Trump’s victory, then the big driver of his gains was persuasion: He flipped millions of white working-class Obama supporters to his side.
The voter file data makes it impossible to avoid this conclusion. It’s not just that the electorate looks far too Democratic. In many cases, turnout cannot explain Mrs. Clinton’s losses.
Take Schuylkill County, Pa., the county where Mr. Trump made his biggest gains in Pennsylvania. He won, 69 percent to 26 percent, compared with Mitt Romney’s 56-42 victory. Mrs. Clinton’s vote tally fell by 7,776 compared with Mr. Obama’s 2012 result, even though the overall turnout was up.
Did 8,000 of Mr. Obama’s supporters stay home? No. There were 5,995 registered voters who voted in 2012, remain registered in Schuylkill County, and stayed home in 2016.
And there’s no way these 2016 drop-off voters were all Obama supporters. There were 2,680 registered Democrats, 2,629 registered Republicans and 686 who were unaffiliated or registered with a different party. This is a place where registered Democrats often vote Republican in presidential elections, so Mr. Obama’s standing among these voters was most likely even lower.
Were they mostly supporters of Bernie Sanders? Unlikely: He was popular among the young, but 67 percent of the 2016 drop-off voters were over age 45, and 35 percent were over age 65. Just 5 percent voted in the Democratic primary in 2016, and 7 percent voted in the Republican primary.
Is it possible that the registered Democrats who turned out were Trump supporters, and that the Democrats who stayed home were likelier to be supporters of Mrs. Clinton? Perhaps, but our polling suggests the opposite. In our pre-election Upshot/Siena polls, voters were likelier than nonvoters to support their party’s nominee.
Survey data, along with countless journalistic accounts, also suggest that voters switched in huge numbers.
Throughout the campaign, polls of registered voters — which are not subject to changes in turnout — showed Mrs. Clinton faring much worse than Mr. Obama among white working-class voters.
The postelection survey data tells a similar story: Mrs. Clinton won Mr. Obama’s white-working class supporters by a margin of only 78 percent to 18 percent against Mr. Trump, according to the Cooperative Congressional Election Study.
In the Midwestern battleground states and Pennsylvania, Mrs. Clinton had an advantage of 76 percent to 20 percent among white working-class Obama voters.
The survey data isn’t perfect. It relies on voters’ accurate recall of their 2012 vote, and that type of recall is often biased toward the winner. Indeed, the C.C.E.S. found that Mr. Obama had 54 percent of support among 2012 voters, compared with his actual 51 percent finish.
But the data all points in the same direction: Shifts in turnout were not the dominant factor in Mr. Trump’s success among white working-class voters.