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Donald Trump's supporters have taken issue with one of the formative documents of the modern US - which ensured the freedom of millions of slaves in the country.

Abraham Lincoln's Emancipation Proclamation, enshrined during the Civil War on January 1, 1863, introduced the banning of slaves in the Southern states.

In a single stroke, it changed the federal legal status of more than three million enslaved people in the designated areas of the South from "slave" to "free".

But a YouGov/Economist poll has revealed that nearly one in five of the Republican presidential front-runner's supporters disagreed with the proclamation.

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The total figure for all respondents was 13% - and "nearly 20% of Trump supporters," the New York Times reports, said they disapproved.

(Image: Getty Images)

The figure compared with 5% of Maro Rubio's supporters, the next most popular candidate who is currently touring the US as part of the presidential primaries.

The other questions first posed by YouGov addressed the use of executive orders - those given by the president to direct federal agencies.

(Image: Reuters)

After answering if they approved of them and if they were constitutional, they were quizzed on their feelings about specific presidential actions, including freeing slaves, desegregating military, interning Japanese Americans during World War II and deferring deportation for some unauthorised immigrants.

Donald Trump says he wants to PUNCH a heckler in the face:

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It's been noted that while the presidential action of Lincoln was one of the great acts of the country's history, it's also controversial in the way he exercised his power of office.