U.S. Sen. Elizabeth Warren says threats to our country's democracy keep her up at night.

And one of the biggest threats comes from the Supreme Court, Warren said on Boston Public Radio Friday morning.

She said the Supreme Court has burned their credibility with recent rulings on abortion, voting rights and affirmative action. But she said their decision to overturn President Joe Biden’s student loan forgiveness plan was "just a gobsmacker," as no plaintiff was involved in the case and, she said, the justices "ignored" language of the statute in order to decide the case themselves.

“They're not just overturning old precedent. They're actually saying 'We're just going to reach out and start substituting our decisions for policy decisions made by Congress. Policy decisions made by the president of the United States,'” said Warren. “The whole idea of separation of powers was the Supreme Court got to go last, but [their scope is] really narrow.”

Warren said the court's actions have been frightening.

Less than half of Americans (44%) express a favorable opinion of the court, showing how out of touch the justices are with the view of most Americans.

To protect democracy, Warren favors expanding the court by adding four justices.

"This court is an extremist court," said Warren. "It has burned its own credibility. It refuses to follow just basic ethics. ... They've taken away constitutional rights. They are aggrandizing power."

Warren said there comes a time when the court is so extremist "it is putting our very democracy at risk." And she said that time is now.

The number of Supreme Court justices changed six times before settling in 1869 on the current total of nine justices. Warren supports another change, bringing the total number of justices to 13.

But until we eliminate the filibuster, Warren said the Supreme Court, abortion or voting rights legislation won't change.

“We now have a major political party in the United States that has openly said the way they intend to keep power is by preventing American citizens from voting or not counting the votes that they actually cast,” said Warren.

Watch Sen. Elizabeth Warren's full appearance on Boston Public Radio: