(CNN) At a rally in Youngstown, Ohio, Tuesday night, President Donald Trump mused on critics who say he doesn't act "presidential" enough .

"It is much easier to act presidential than what we are doing here tonight, believe me," Trump assured his audience. "With the exception of the late, great Abraham Lincoln, I can be more presidential than any president that's ever held this office."

Well then.

Lincoln has frequently been singled out for praise by Trump and used as a point of reference when he is when pondering the impact of his own presidency.

"Great president," Trump said of Lincoln in March of this year. "Most people don't even know he was a Republican. Right? Does anyone know? A lot of people don't know that. We have to build that up a little more."

A year earlier -- in April 2016 -- Trump said this of Lincoln in an interview with the Washington Pos t: "I can be very presidential. I jokingly say, I can be more presidential than any president that this country has ever had except for Abraham Lincoln, because he was [unclear]. Right? You can't out-top Abraham Lincoln."

"Jokingly." Ahem.

It's impossible to fact-check Trump's claims to being more "presidential" than anyone but Lincoln since no sort of grading system of the 44 men who have been president includes such a subjective measure.

In those rankings, which are determined by the collective views of a group of historians, Lincoln has been ranked as the best president in history in each of the three years (2000, 2009, 2017) C-SPAN has conducted the survey. George Washington finished second in 2017 and 2009 and third in 2000. Franklin Delano Roosevelt has been third in the last two C-SPAN survey but was second in 2000.

The highest ranking modern president is Barack Obama who comes in 12th in the 2017 survey. Bill Clinton is 15th -- the same spot he held in 2009 but up 6 spots from his initial ranking in 2000.

The lowest ranked modern president is George W. Bush at 33rd in 2017, up from 36th in 2009. The worst-rated president overall is James Buchanan, who served from 1857 to 1861. (Trump wasn't included in the C-SPAN survey since he only assumed the presidency in January 2017.)

While there is no ranking of the presidents by "presidential-ness" in the C-SPAN survey, there are rankings of each man in 10 specific categories considered essential to presidential success (or failure).

On "public persuasion " -- which is kind of like being "presidential" -- FDR is ranked No. 1 followed by Teddy Roosevelt, Lincoln, Washington and Ronald Reagan. (Clinton is 9th. Obama is 10th. Bush is 25th.)

On "vision/setting an agenda" -- again, sort of "presidential" -- the top 5 goes like this: Lincoln, Washington, FDR, Teddy Roosevelt and Thomas Jefferson. (Obama is 12th, Clinton 19th, Bush 26th.)

On "moral authority" -- another piece of being "presidential" -- it's Washington, Lincoln, FDR, Dwight Eisenhower and Teddy Roosevelt. (Obama is 7th, Bush is 34th and Clinton is 38th.)

In short: If Trump wants to slide into the second spot behind Lincoln, he's got some work to do. Look out George Washington!