As the dust clears from Donald Trump’s shocking victory to become the 45th president of the United States, humbled political prognosticators and pollsters have been trying to piece together what went wrong for Hillary Clinton. Much of the post-election analysis, often based on limited exit poll data, indicated that Clinton lost the Electoral College because members of minority communities did not vote in high enough numbers. There is some truth to this explanation, especially in North Carolina, where the state closed polling places in African-American areas.

But a closer look at vote totals reveals another possible explanation for what happened — namely, that tens of thousands of white Democrats in key states just stayed home this year.

With the help of a USA Today map showing changes in turnout by county, we looked at the six states that flipped from blue in 2012 to red in 2016. Turnout was largely up across Michigan, Florida, and Pennsylvania. But in Ohio, Wisconsin, and Iowa, 11 counties saw voter turnout decline by at least 5 percent.

Nine of those counties had striking similarities: They were overwhelmingly white and saw a drop in votes for Democrats by the thousands even as Republican vote totals remained relatively unchanged. These missing white Democrats helped doom Clinton.

The table above offers a breakdown of Democratic and Republican vote totals in the 11 low-turnout counties. In each case, we compared the certified state results from 2012 to the unofficial 2016 Associated Press totals published by Politico since many state totals aren’t certified yet. One important note: County-level data on changes in turnout was incomplete for every state we examined except Pennsylvania. In some cases information on as many as 31 percent of counties was missing. As a result, we have a snapshot and not a comprehensive analysis.

Among the counties we examined, Wisconsin’s Menominee County was one of the two that did not fit same demographic profile as the rest. It is 80 percent Native American with fewer than 1,500 voters (Trump won 269 of them compared to Mitt Romney’s 179). The other, Milwaukee County, has been held up by Democrats including Obama campaign manager David Plouffe as an example of how low African-American turnout drove Trump to victory. But vote totals in Milwaukee County were depressed by similar proportions among both Democrats and Republicans.

The bigger problem for Clinton was her performance in the state’s largely white counties. In Rock County, Wisconsin, which is 90.7 percent white, Clinton received almost 10,000 fewer votes than Obama while Trump got about as many as Romney did. Other heavily white counties — including Iowa’s Clinton County — saw similar drop-offs among Democrats.

No single metric can explain Trump’s unprecedented upset victory. Turnout in three of the six flipped states was up and some Democrats who voted for Obama in 2012 voted for Trump in 2016. African-American turnout appears to have fallen in some areas. But in the states that flipped from blue to red, the counties with the largest turnout decline were full of white Democrats.