BERKELEY, Calif. — In explaining why it had canceled a speech by Ann Coulter scheduled for next week, the University of California, Berkeley, said that it had “very specific intelligence” that Ms. Coulter might be in “grave danger.”

To Ms. Coulter and her supporters, it was another example of Berkeley showing intolerance of any opinions other than the liberal ones it is famous for. But the university that championed free expression in the 1960s has become known, in the polarizing first months of the Trump presidency, as something more: a meeting ground for those wanting to express themselves with wooden clubs and fists.

Days after fights broke out between anarchists and right-wing groups near campus, and a couple of months after masked protesters smashed windows and set fires to stop a speech by the incendiary right-wing writer Milo Yiannopoulos, the police are preparing for a possible replay if Ms. Coulter follows through on her vow to show up anyway on Thursday.

“The city and campus have become the stage on which the national political tensions are playing out,” said Dan Mogulof, a spokesman for the university. “Coming here, they know they will be able to find an opponent pretty easily.”