Huffington also criticized Trump for comments he made last week on MSNBC about abortions. He said if the procedures were illegal, women who have them should face "some form of punishment." Trump's campaign later released a statement clarifying the remark.
"The media are very responsible for the rise of Trump," she said. "Republics have been destroyed by demagogues."
As Wisconsin voters head to the ballot boxes on Tuesday for the state's Republican presidential primary, Texas Sen. Ted Cruz leads the billionaire businessman Trump in the polls. Ohio Gov. John Kasich remains a distant third.
If Cruz were to win all of Wisconsin's 42 delegates, Trump would need to win 57 percent of the remaining delegates to clinch the nomination before this summer's convention.
"I disagree with Ted Cruz, but I don't consider him an unstable, dangerous force for America," Huffington said.
She spoke most highly of Kasich.
"You see John Kasich, he's going a very good job of maintaining a civil tone and appealing to the best in people. And he's not doing very well in the polls."
The Huffington Post's parent company is AOL, which is owned by Verizon.