Despite being impeached twice, former President Donald Trump is not the worst president in U.S. history, according to 142 presidential historians surveyed by C-SPAN, the results of which were released Wednesday. 

But the survey doesn't give Trump much to brag about either. He ranked lower than William Henry Harrison, who was president for only 31 days, and John Tyler, the only former president buried in a coffin draped with the Confederate flag.

So who ranked worse than Trump? According to the historians, presidents Franklin "Bleeding Kansas" Pierce, Andrew "First to Be Impeached" Johnson and James "Failed to Stop the Civil War" Buchanan, who came in last.

To be clear, this was an informal survey whose respondents were selected by C-SPAN, not a scientific poll. Dozens more historians were invited to complete the survey this time than in years past. C-SPAN said this was to reflect "new diversity in race, gender, age and philosophy," but that also makes it harder to compare it to previous surveys.

Still, the respondents are all distinguished presidential historians covering a broad range of perspectives, and there are insights to gain from their collective opinions.

Even with all the new historians participating, the top and bottom rankings remained unchanged. Since 2009, the top four presidents have been: 1. Abraham Lincoln, 2. George Washington, 3. Franklin D. Roosevelt and 4. Theodore Roosevelt. (Washington and FDR switched places in the 2000 survey.) The bottom three have been always been Pierce, Johnson and Buchanan, in that order.

The survey is conducted only when there is a change in administration, so that each presidency can be evaluated in its entirety. The historians do not rank the presidents themselves. Instead they are asked to rate each president from 1 to 10 on 10 leadership categories; the averages of all of the ratings are then ranked. The 10 categories are public persuasion, crisis leadership, economic management, moral authority, international relations, administrative skills, relations with Congress, vision/setting an agenda, pursuit of equal justice for all and performance within the context of the times.

Trump got his best average rating on public persuasion, in which he came in 32nd. On moral authority and administrative skills, however, he came in dead last.

Alexis Coe is one of the historians invited to do the survey for the first time, after her well-regarded 2020 book "You Never Forget Your First: A Biography of George Washington." In her newsletter, she said she "jumped for joy" when she received the survey, then "agonized over every rating" for months. What about vision/setting an agenda for James K. Polk, who brought enslaved people to the White House and also annexed Texas? Warren G. Harding certainly rates low on moral authority, she wrote, but how low for his policies and how low for cheating on the first lady?

"I've yet to study a president who's a perfect 10," Coe wrote.

The president whose reputation has improved the most in the past two decades? That's Ulysses S. Grant, who started at No. 33 and is now ranked 20th. Grant has had a number of sympathetic biographies in recent years, and these days gets more credit for Reconstruction and his diplomacy than condemnation for his alleged corruption.

No president has fallen quite as much as Grant rose in the same period; but Trump favorite Andrew Jackson fell the most, from No. 13 to No. 22. It is perhaps a reflection of changing attitudes in the public. Soon Jackson may fall right off the $20 bill.

Other interesting patterns reveal themselves in the rankings. The five presidents from 1933 to 1969 - FDR, Harry S. Truman, Dwight D. Eisenhower, John F. Kennedy and Lyndon B. Johnson - rank in the top 11, making it the best stretch of presidents historians say America has had. The worst stretch came from 1837 to 1869, with the notable exception of four-time champion Lincoln.

In 2017, former President Barack Obama entered the ranking at No. 12, though Howard University historian Edna Greene Medford warned The Washington Post at the time that "historians prefer to view the past from a distance, and only time will reveal his legacy." Four years later, a little distance seems to be doing Obama's legacy good; he is now ranked No. 10.

President Joe Biden will not be included in the C-SPAN survey until he has left office.

C-SPAN is not the only outfit conducting presidential rankings, and other recent surveys have included Trump before he left office. In 2018, when Boise State University surveyed presidential scholars for its Presidents & Executive Politics Presidential Greatness survey, Trump came in last. And that was before the two impeachments, the coronavirus pandemic and the Capitol insurrection.