President Donald Trump arrives at Palm Beach International Airport, Florida, Apr. 13, 2017. Reuters

The man who accurately predicted that Donald Trump would become president of the United States had another prediction to share about Trump’s future in office. Allan Lichtman, a professor at American University, shared an advance copy of his book “The Case For Impeachment” with Politico Friday.

The professor, who used a formula that correctly predicted the outcome of eight previous elections, predicted Trump would be impeached, though he said the president seemed to have missed that and focused instead on his correct prediction of Trump’s win.

“Taking time out of preparing to become the world’s most powerful leader, he wrote me a personal note, saying ‘Professor —Congrats — good call,’ read an excerpt of Lichtman’s book. “What Trump overlooked, however, was my ‘next big prediction’: that after winning the presidency, he would be impeached."

The professor, who denounced many of Trump’s policies in the book, offered the president advice to avoid that very prediction coming true.

“Opponents will challenge your decision-making abilities and claim that they were right all along about your temperamental unfitness for presidency, yet you have survived and thrived by defying the conventional political wisdom,” Lichtman wrote. “Why not do it again?”

He suggested Trump divests himself of his business interests, employ a fact-checker, support the Paris Climate agreement and start treating women with more respect, according to Politico.

“Justice will be realized in today’s America not through revolution, but by the Constitution’s peaceful remedy of impeachment,” he wrote. “But only if the people demand it.”

Lichtman is not alone in his prediction. BetOnline.ag, a popular betting website tracking Trump’s impeachment odds, said earlier in April that there was a mere 40 percent chance the president would still be in office by the time the next election rolled around.

Trump’s popularity seemed to be waning as well. A Gallup poll released Thursday showed that 55 percent of respondents disapproved of the president, while 40 percent approved of the job he was doing.

President Donald Trump waves as he boards Air Force One at Joint Base Andrews outside Washington, D.C., Apr. 13, 2017. Reuters