Way back in September, when most pundits were gleefully speculating about whether the Republican Party would ever recover from the Electoral College shellacking in store for then-candidate Donald Trump, one man had a very different guess about how things would shake out. Allan Lichtman, a history professor at American University in Washington, D.C., declared Trump to be the favorite, relying on an election prediction methodology he had developed some three decades earlier and used to correctly predict every presidential election since. Lichtman was, of course, extremely correct—an accomplishment that earned him a personal note from the president-elect just a few days after the election. "Professor—congrats," wrote Trump in a letter to Lichtman. "Good call."

Around that same time, though, the vindicated prognosticator already had another fearless forecast ready to go, one that the president-elect would presumably not appreciate as much: Trump, Professor Lichtman asserted with confidence, will become only the third President of the United States to be impeached. He makes his case in a new book, The Case for Impeachment, and we spoke to him last week about how the country got to this point, and why he feels just as confident about this prediction as he was with the last one.

GQ: What made you feel confident predicting Trump's victory as early as you did?

Allan Lichtman: By paying no attention to the polls, or the pundits, or the day-to-day events of the campaign—the things that led most forecasters to arrive at erroneous conclusions. Instead, I used my system, the “Keys to the White House,”, which I first developed in 1981 and have used to correctly predict the nine presidential elections since. The basic thesis is that you have to keep your eye on the big picture of the strength of the incumbent president’s party. This time, the Democrats had many vulnerabilities irrespective of who their candidate was, or anything that either side did during the campaign. The party took a pasting in the 2014 midterms; the sitting president couldn’t run again; they endured a contentious primary fight; they didn’t follow up the Affordable Care Act with a big policy initiative during President Obama’s second term; and so on. A presidential election is, at its core, a referendum on whether the party in power should get four more years in office.

Having made that prediction, what makes you now think he’ll be impeached?

My impeachment prediction is not based on a formal methodology—after all, we’ve only had two impeachments, or three, including President Nixon’s resignation. But it is based on a deep study of history, including Trump’s parallels to his impeached predecessors; a study of the process of impeachment; a study of Trump's vulnerabilities, particularly those that have arisen over the course of his business career; and a look at the early weeks of his tenure in the White House. I identified eight separate grounds on which Trump is arguably susceptible to impeachment or removal, and I believe he is more vulnerable than any early president in the history of the nation.

Why release the book now, as his presidency unfolds and the already-murky details of his alleged malfeasance seem to grow more complicated by the day?

I thought very carefully about that. In the age of Trump, the pace of everything is accelerated—he’s been president for less than 100 days, and we feel like he’s been president for years.

But I’m not aiming to scrutinize the day-to-day events of the presidency. Instead, I wanted to provide a road map in the event that he does cross that line—because impeachment is a political process that occurs outside of the courts. It is responsive to the people, and if impeachment is going to take place, it will be because the American people demand it. All these protests and demonstrations and energy directed against the Trump presidency will be like smoke through a chimney unless, eventually, they are directed at achieving a specific political end.