Americans generally hold this truth to be self-evident: George Washington and Abraham Lincoln were presidents who earned their places on monuments and on currency through exemplary leadership that united the country.

That reverence is celebrated every year on Presidents Day — a national celebration observed in one form or another since President Rutherford B. Hayes signed an 1879 law establishing a federal holiday on Feb. 22, the anniversary of Washington's birth.

That reverence now seems quaint, a phenomenon relegated to larger-than-life figures from a distant past when powdered wigs or stove-pipe hats were in vogue.

A closer look at history, however, shows that no president has managed to leave the position without alienating a large segment of the populace. Partisan bickering has been an American tradition since the flag had 13 stars, well before 140-character tweets.

"We look back without rancor at these guys, but Washington was bitterly denounced during his presidency and the language used against Lincoln makes what’s said against Trump very mild," Eric Foner, DeWitt Clinton Professor Emeritus of History at Columbia University, told NBC News.

"The partisan bitterness that we see today is not unprecedented by any means."

History suggests that with time and perspective, one or more recent presidents could find themselves, if not carved on Mount Rushmore, then at least mentioned in the same breath as those immortalized in granite.

And political biases aside, historians caution that it is difficult to gauge which presidents will go down in history as greats, because the true impacts of many of their policies and decisions aren't clear until later.

"Harry Truman left office with historically low ratings, but most historians would now rate him as one of the greats," said Barry Bradford, distinguished lecturer for the Organization of American Historians.

"Historical legacy usually improves over time. But it takes time and space."

Washington is an example of how all the monument-making can sand down the less favorable or controversial legacies of a plantation owner who owned slaves.

Considered by many historians and lay folk to be the most influential figure in American history, Washington's reputation was buttressed by his role leading the Continental Army to victory over the British during the Revolutionary War.

It's a legacy that has been amplified over time, said best-selling author Brad Meltzer, whose latest book, "The First Conspiracy," chronicles a little-known assassination attempt on then-General Washington during the early days of the war.

"We love to tell the story of Washington the great general, but in his earliest battles he would routinely get out-generaled," Meltzer said. "He just didn’t have the experience of the British.

"We are a country that loves legends and myths, and the myths we love the most are our own."

Over time, Lincoln has become as heralded as Washington — at least in the parts of the country on the winning side of the Civil War.

That's probably why Lincoln's Feb. 12 birthday never became a national holiday, though many celebrate it as part of Presidents Day after the passage of the Uniform Monday Holiday Act in 1971.

"In the South, there’s considerable reservation about Lincoln," Foner said. "While many associate him primarily with the emancipation of slaves, there is a neo-Confederate element that views Lincoln as a tyrant who suppressed states rights, introduced the income tax and suspended habeas corpus."

While it's hard to evaluate the future legacy of a president — including Trump or Obama — during their lifetimes, American history has shown certain patterns.

Presidents who are assassinated tend to be romanticized with an added mystique. "John F. Kennedy is widely admired by Democrats and Republicans nowadays, on rankings of the greatest presidents, Kennedy usually right up at the top, even though his presidency is rather short in length and accomplishment," Foner said.

Steering a country through a major war or crisis is also a selective legacy booster, which explains the popularity of Franklin D. Roosevelt despite his role in the internment of Japanese Americans at the time. Roosevelt presided over the U.S. during World War II.

Modern presidents, however, may have a tougher path to that level of popularity than their predecessors. And it comes back to those tweets.

"The advent of social media and blogging make it less likely that a consensus could be reached," Bradford said. "In an era in which we depended on the 'Huntley-Brinkley Report' or Time magazine to tell us what’s going on, we didn’t believe that every opinion is equal.

"In order to have that popular consensus, we have to rebuild trust in media and historical thinking generally. If we are told constantly that what we read is 'fake news,' how do we agree on what's real?"

Meltzer, though, believes that the past shows Americans can look forward to the future if they're not so bullish on the present.

"If history proves one thing, in our worst moments we get our best heroes," said Meltzer, who hosted the TV show "Lost History."

"Right now in a supermarket, there is a kid pulling the Cheetos off the shelf, and throwing a tantrum," he said, "and that kid one day will grow up to be president and do something amazing."