A professor who has accurately predicted the winner of eight of the last nine presidential elections says 2020 is still officially “too close to call.”

“This is a very close and very difficult call. I don’t think either the Democrats or the Republicans should be sending up any victory flags at this point,” Allan J. Lichtman, a political historian at American University, told The Post. “Too much is still up in the air and in the age of Trump, things can change very quickly.”

Lichtman, 72, has become a cult figure in American politics for developing a set of 13 criteria which he has used to make his prediction. Metrics include things like scandal, foreign military failure and social unrest. The theory is laid out in his 1996 book “The Keys to the White House.” The system was able to predict Ronald Reagan’s 1984 reelection back in 1982 — during a recession.

(In 2000, he predicted Al Gore would win the popular vote, though tripped up on the ultimate outcome of the electoral college. Something he still doesn’t accept. “2000 was a stolen election,” he says.)

Lichtman predicted Donald Trump’s presidential upset back in September 2016, saying it was one of the toughest calls he’s ever had to make. The prediction raised eyebrows as Hillary Clinton consistently led in most state and national polls. Shortly after Trump’s election, he also said impeachment would be likely — calling it a gut feeling.

Lichtman says Trump’s impeachment doesn’t doom his chances of a second term — but also won’t help him either.

“The party holding the White House would have to lose six keys to count them out. If you add in the inevitable impeachment, that would be a fourth key,” he said, adding that fallout from the vote and a subsequent Senate trial could eventually lead to other keys being met.

Lichtman said he expected an acquittal by the Senate and declined to predict who the ultimate 2020 Democratic nominee would be.

The professor, a vocal Trump critic, had advocated for impeaching the president long before his now infamous phone call with Ukrainian president Volodymyr Zelensky. In April, 2017 he published “The Case for Impeachment” laying out his view that Trump had to go.

Lichtman told The Post he was glad to see the House moving ahead with impeachment saying it was good for the country.

“If he’s not held accountable, he’s just going continue what he’s been doing and you will set a precedent for any future president to rig elections by working with a foreign nation,” Lichtman said.

“Even if it doesn’t result in conviction in the Senate, a real red flashing warning sign will be put up. Otherwise our democracy could go down in flames.”