And their policies often become harsher as well as broader, Mr. van der Maat said, as leaders climb what he called “the ladder of violence” — moving from discrimination into more significant persecution.

Large-scale deportations, such as those Mr. Trump promised on the campaign trail, would be a step higher on that ladder, Mr. Van der Maat said, because they would require the use of force and affect a wide segment of the population. The president last week signed an executive order that would give law enforcement officials expanded resources for carrying out deportations, and promised to punish “sanctuary cities” that refuse to cooperate with federal deportation efforts.

Testing the limits of power

Mr. Trump is a democratically elected president, and the United States is a democracy. But the experts caution that does not mean that the lessons of authoritarian behavior should be ignored entirely.

Presidents Recep Tayyip Erdogan of Turkey and Vladimir V. Putin of Russia, Mr. Weiler said, were democratically elected, then systematically undermined democratic checks and balances to consolidate their own power.

Leaders with authoritarian tendencies “will push and push until they find a spot where they can’t push anymore — and if they don’t, they’ll keep going,” Ms. Berman said. “We’re watching that process happen in not-so-slow motion in Turkey now,” she said, where Mr. Erdogan has “eroded the democratic system to the point where most analysts think it’s no longer democratic at all.”

Mr. Trump’s refugee ban, if it is found to be legal, is not necessarily a step toward that kind of democratic decline, Ms. Berman said. The key thing to watch for, she said, is whether he will try to use the power of the presidency to push through illegal rules or overrule checks and balances.

That has not yet occurred. But the ban is a sign that Mr. Trump is willing to push the limits of the norms of American governing. By circumventing normal procedures for drafting and issuing executive orders, the White House created confusion and chaos within the agencies that will enforce the new rules. On Monday, Acting Attorney General Sally Q. Yates said she did not think the ban was legal and directed the Justice Department not to defend it. Mr. Trump fired her later that day.