Few prognosticators predicted a Donald Trump victory ahead of Tuesday night. Polls showed Hillary Clinton comfortably ahead, and much of America (chiefly the media) failed to anticipate the wave of pro-Trump support that propelled him to victory. But a Washington, D.C.-based professor insisted that Trump was lined up for a win – based on the idea that elections are “primarily a reflection on the performance of the party in power.”

Professor Allan Lichtman uses a historically based system of what he calls “keys” to predict election results ahead of time. During conversations in September and October, he outlined how President Obama’s second term set the Democrats up for a tight race.

At the end of September, Lichtman made another call: That if elected, Trump eventually would be impeached by a Republican Congress that would prefer a President Mike Pence – someone whom establishment Republicans know and trust.

“I’m going to make another prediction,” he said. “This one is not based on a system, it’s just my gut. They don’t want Trump as president because they can’t control him. He’s unpredictable. They’d love to have Pence – an absolutely down the line, conservative, controllable Republican. And I’m quite certain Trump will give someone grounds for impeachment, either by doing something that endangers national security or because it helps his pocketbook.”

Lichtman actually isn’t the only person to predict a Trump impeachment. Friday morning, The New York Times’ David Brooks suggested a Trump impeachment or resignation was “probably” in the cards within the next year.

Some statisticians take issue with Lichtman’s system, a set of 13 true/false questions, saying that the binary nature of his keys creates a system that fits the data but has little statistical significance. But Lichtman counters by saying that his system has correctly predicted every election since 1984 except for 2000, when he picked Al Gore, who won the popular vote, as did Clinton.