The New York Times took a dive into whether Donald Trump's supporters are unusually racist — or, in the newspaper's delicate phrasing, "responsive to religious, social and racial intolerance." And they came up with a stunning statistic: Nearly one in five Trump supporters didn't approve of freeing slaves in the Confederacy.

A YouGov/Economist poll in January asked respondents if they approved or disapproved of "the executive order that freed all slaves in the states that were in rebellion against the federal government."

That executive order is better known as the Emancipation Proclamation. Thirteen percent of respondents — and "nearly 20 percent of Trump supporters," the Times reports, compared with 5 percent of Marco Rubio's — said they disapproved of it.

It gets even worse. An additional 17 percent of respondents said they weren't sure.

Before asking about slavery, YouGov first asked two broader poll questions about executive orders: Do you approve of them, and do you think they're constitutional? Then they asked about specific presidential actions, including freeing the slaves, desegregating the military, interning Japanese Americans during World War II, and deferring deportation for some unauthorized immigrants.

Framing the question this way is a reminder that one of Lincoln's greatest acts, and a turning point in American history, was also a controversial exercise of presidential power. And it's stunning how many people can't bring themselves to say they approve of it.