US President Donald Trump speaks on the Florida school shooting, in the Diplomatic Reception Room of the White House: AFP/Getty Images

Nearly 200 of America's top political scientists have voted Donald Trump the worst president in US history.

According to the 2018 Presidents & Executive Politics Presidential Greatness Survey, Mr Trump ranks even lower than disgraced President Richard Nixon – even among conservatives. Abraham Lincoln, unsurprisingly, takes the top prize. Mr Nixon sits at 33.

The study, conducted every four years, surveys social science researchers from the American Political Science Association’s section on presidents and executive politics. It asks the experts to rank each president’s greatness on a scale of 0 to 100, with 100 being great, 50 being average, and 0 being a total failure.

Mr Trump averaged a score of 12.34, bumping James Buchanan – the president who saw the US descend into the Civil War – out of the bottom spot. The result comes just months after Trump finished his first year in office as the most unpopular president in modern history.

Mr Trump’s predecessor, Barack Obama, jumped 10 places since the survey was last conducted in 2014, to spot number eight. George W Bush also climbs in the rankings, making it five places up to number 30.

Bill Clinton did not fair was well as the other living presidents, dropping five places down to 14th. Only Andrew Jackson dropped more – down six places – possibly owing to increased attention on how he treated Native Americans.

The top seven presidents remained the exact same, with Abraham Lincoln on top, followed by George Washington, Franklin Delano Roosevelt, Theodore Roosevelt, Thomas Jefferson, Harry Truman and Dwight Eisenhower.

Mr Trump was accompanied in the bottom five by Andrew Johnson, Franklin Pierce, William Harrison, and Mr Buchanan.

Researchers Brandon Rottinghaus, of the University of Houston, and Justin Vaughn, of Boise State University, said they surveyed 170 political science experts for the study. Of those experts, 57.2 per cent identified as Democrats, 12.7 per cent as Republicans, and 27.1 per cent as independents.

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While Republicans and Democrats differed on how they viewed figures like Mr Obama and Mr Bush, they were in fairly close agreement on My Trump: Conservatives voted him 40th out of 45.

The one area where Mr Trump did come out on top was in the “most polarising” section, in which the researchers asked the scientists to list the five presidents they found most divisive. Mr Trump was ranked most polarising by 90 of the 170 respondents, and second-most polarising by another 20.