Donald J. Trump rose to power with political campaigns that largely attacked external targets, including immigration from predominantly Muslim countries and from south of the United States-Mexico border.
But now, in his third presidential bid, some of his most vicious and debasing attacks have been leveled at domestic opponents.
During a Veterans Day speech, Mr. Trump used language that echoed authoritarian leaders who rose to power in Germany and Italy in the 1930s, degrading his political adversaries as “vermin” who needed to be “rooted out.”
“The threat from outside forces,” Mr. Trump said, “is far less sinister, dangerous and grave than the threat from within.”
This turn inward has sounded new alarms among experts on autocracy who have long worried about Mr. Trump’s praise for foreign dictators and disdain for democratic ideals. They said the former president’s increasingly intensive focus on perceived internal enemies was a hallmark of dangerous totalitarian leaders.
Scholars, Democrats and anti-Trump Republicans are asking anew how much Mr. Trump resembles current strongmen abroad and how he compares to authoritarian leaders of the past. Perhaps most urgently, they are wondering whether his rhetorical turn into more fascist-sounding territory is just his latest public provocation of the left, an evolution in his beliefs or the dropping of a veil.
“There are echoes of fascist rhetoric, and they’re very precise,” said Ruth Ben-Ghiat, a professor at New York University who studies fascism. “The overall strategy is an obvious one of dehumanizing people so that the public will not have as much of an outcry at the things that you want to do.”
Mr. Trump’s shift comes as he and his allies devise plans for a second term that would upend some of the long-held norms of American democracy and the rule of law.