What will happen to President Barack Obama's legacy now that businessman Donald Trump is president-elect and will be entering the White House with a Republican controlled Congress?

According to Fox News commentator Charles Krauthammer, Obama's legacy is "toast."

Krauthammer explained during a recent interview with Fox host Megyn Kelly that the reason why Obama campaigned so hard for Democrat Hillary Clinton and against Trump is because he knew what would happen to his legacy if Trump won.

"Obama's legacy is gone, which explains why he so desperately — and unusually in American history — campaigned so roughly against Donald Trump," he said.

Krauthammer went on to explain that Obama knows that much of his legacy was built by "ramming" legislation through Congress — such as Obamacare — and through executive orders, which are easily reversible.

"He thought he was the Ronald Reagan of the left," Krauthammer said. "Obama thought he would begin a liberal ascendancy the way that Reagan began a conservative ascendancy."

"Well, it did not turn out that way," he added. "The country rejected his policies."