Wanna know something scary? Close to 20 percent of voters supporting Republican presidential candidate Donald Trump don't think Abraham Lincoln's decision to free enslaved Africans during the Civil War was the right thing to do, according to a recent Economist/YouGov poll.

Now the January survey doesn't provide a perfect measurement of voters' racism. Some of those people might have been sticklers for a certain kind of procedure, even when it came to slavery.

Taken in the aftermath of President Barack Obama's executive actions on gun control, the survey asked respondents about the constitutionality of executive orders in general and their use by presidents. Then it asked whether respondents "approve or disapprove of the executive order which freed all slaves in the states that were in rebellion against the federal government."

So it's possible that some who disapproved were objecting to what they saw as presidential or federal overreach rather than freedom for black people.

Trump supporters are also more likely than Republicans as a whole to oppose the use of executive orders, which President George Washington began issuing, and to consider them unconstitutional.

I see no problem with banning Mexicans, tracking potential terrorists & if I had a slave life would be easier! https://t.co/vp6AKyplLS — Riv (@StopRiv2016) February 24, 2016

"Slavery fans" = no self-hatred

"Banning Mexicans" = Mexicans stay in Mexico

"Tracking Muslims" = National security https://t.co/Rjg8H0jwcu — Dєг Ӎaгӿіstєпјӓgєг ⊕ (@MrJohnQZombie) February 24, 2016

In case you're curious, the survey found that 70 percent of Americans overall approved of the Emancipation Proclamation, 13 percent disapproved, and 17 percent weren't sure.

Trump's appeal among white Republicans is crystal-clear. He dominated in the Nevada GOP caucus on Tuesday, winning 46 percent of the vote overall and claiming his third straight win (following New Hampshire and South Carolina). Keep in mind that this is the man who has labeled Mexican immigrants as "criminals" and "rapists," advocated banning Muslims from the U.S., referred to black people as "thugs" and repeatedly used sexist language.

Couple this with the sometimes violent response that Trump's non-white opponents receive at his rallies, and it should be no surprise that a sizable group of his supporters didn't shy away from the racial bigotry implied by their survey answer.