In the year since Hillary Clinton’s shocking loss in the 2016 election, what have Democrats learned about how and why Donald Trump won? And what does his victory mean for the future of the Democratic Party? A new report from the Center for American Progress, a Washington think tank that was closely allied with both the Obama Administration and the Clinton campaign, proposes some answers to these questions.

Drawing on Census Bureau data and the results of other public surveys, and of exit polls, the report shows in great detail how Trump, who effectively ran as a white-identity politician, offset the demographic changes—particularly the rising proportion of nonwhite voters in the electorate—that Clinton and other Democrats believed gave her an edge. The authors of the study—Robert Griffin, Ruy Teixeira, and John Halpin—argue that the two keys to Trump’s narrow victory in the Electoral College were a rise in turnout and support levels among non-college-educated white voters, and a fall in turnout among some minority groups relative to 2008 and 2012. Absent either of these factors, the report says, the election result might have been different.

“If black turnout and support rates in 2016 had matched 2012 levels, Democrats would have held Florida, Michigan, Pennsylvania, and Wisconsin and flipped North Carolina, for a 323 to 215 Electoral College victory,” Griffin, Teixeira, and Halpin write. “So increasing engagement, mobilization, and representation of people of color must remain an important and sustained goal of Democrats.”

At the same time, the authors suggest that Trump could conceivably win reëlection in 2020 if Democrats don’t do a better job of appealing to the less affluent whites who flocked to Trump last year. “Given the fact that the white non-college-educated voting population is almost four times larger as a share of the electorate than is the black voting population,” the report notes, “it is critical for Democrats to attract more support from the white non-college-educated voting bloc—even just reducing the deficit to something more manageable, as Obama did in 2008 and 2012.”

None of the report’s authors worked for a Presidential campaign last year, but Teixeira co-wrote “The Emerging Democratic Majority,” an influential 2002 book that highlighted the growing number of minority voters, and particularly of Latino voters, across the country. The proportion of whites among all eligible voters has continued to decline—it dropped by a percentage point, or so, between 2012 and 2016—and the new report explores how Trump countered this trend. By mobilizing whites, particularly those without college degrees, Trump managed to keep the decline in the actual white-vote share to just 0.3 points, the report says.

“None of this means demographic change isn’t a significant plus for the Democrats,” Teixeira explained to me in an e-mail. “It is and will continue to be. But it is a plus, not a guarantee. If the Republicans can continue to increase their margins among white non-college voters, as they have for several elections, demographic change by itself is certainly not enough to dislodge the GOP. Conversely, if the Democrats can shave the margin the Republicans attain among white non-college voters they will be in very good shape, partially because the direction of demographic change is in their favor.”

Of course, the fact that Trump was popular among working-class whites isn’t news. But Teixeira and his colleagues claim that the exit polls understated the over-all white-vote share, putting it at seventy-one per cent, compared with their estimate of 73.7 per cent. In a close election, a difference of 2.7 points in the voting share of a key demographic can make a big difference. The study’s findings appear to confirm the analysis of observers such as Sean Trende, of Real Clear Politics, and Nate Cohn, of the Times, who argued during the campaign that there could be more white voters than most people realized.

Of at least equal importance, Griffin, Teixeira, and Halpin also claim that, within the over-all white vote, the polls seriously underestimated the proportion of people without a college degree—a group that voted for Trump over Clinton by a margin of twenty-five points, the study finds. “The exit polls claimed that white college graduates actually outnumbered non-college-educated white voters at the polls in 2016, 37 to 34 percent,” the report says. “Our data indicate a vastly different story: white college graduates were only about 29 percent of voters, while their non-college-educated counterparts far outdistanced them at 45 percent of voters.”

If the report’s higher estimate for the number of non-college-educated white voters is accurate, it is easier to explain how Trump got 46.1 per cent of the popular vote. Nobody has ever doubted his appeal to voters in this demographic, and the study also shows how they helped him eke out a narrow victory in the Electoral College, despite his substantial loss in the popular vote. In Michigan, Pennsylvania, and Wisconsin, the proportion of white non-college-educated voters was fifty-four per cent, fifty-four per cent, and fifty-nine per cent, respectively, the study finds. (By contrast, the exit polls said that white non-college-educated voters were in the minority in these states.)

White non-college-educated voters were also central to Trump’s victory in other battleground states, such as Florida and North Carolina, the report finds. In Florida, the white non-college-educated turnout rose by seven points relative to 2012, which was enough to keep the white vote steady despite substantial demographic changes. Something similar happened in North Carolina, where white non-college turnout also increased.

As the race progressed last year, the people running the Clinton campaign were well aware that Trump was mobilizing his white base in dramatic fashion. Where they may have erred was in assuming that his offensive and incendiary remarks about immigrants and members of minority groups would produce a parallel mobilization behind Clinton. As the new report illustrates, this didn’t happen.

Relative to 2012, the African-American turnout rate fell by 4.5 points. Among blacks who did vote, Trump’s losing margin was 79.9 points, compared with Mitt Romney’s 87.9 points. Obviously, the fact that Barack Obama was no longer on the ballot played a big role here. More surprisingly, perhaps, the study confirms the exit polls’ finding that more than one in four Latinos voted for Trump: it puts the exact proportion at 28.7 per cent. Despite the fact that Trump campaigned on a platform of deporting undocumented immigrants en masse, he narrowed the Republicans’ losing margin among Latinos from 39.3 points in 2012 to 36.5 points in 2016, the report finds.

It will be interesting to see if other researchers challenge these numbers, or any of the others in the report. (Immediately after the election, some Hispanic groups claimed that the exit polls had overestimated how many Latinos voted for Trump.) What can’t be disputed is the fact that Democrats need a strategy to retake the White House in 2020. The authors of the report believe that the Party “must go beyond the ‘identity politics’ versus ‘economic populism’ debate to create a genuine cross-racial, cross-class coalition that supports economic opportunity, good jobs, and decent social provisions for all people and makes specific steps to improve the conditions of people of color, many of whom continue to suffer from the legacy of historical and institutional racism.” This sounds reasonable. It also echoes some of what Hillary Clinton said last year. The Democrats have a big challenge ahead.