A YEAR ago, just after he said he favored requiring Muslims in the United States to register in a government database, Donald Trump was asked how that would differ from Nazi Germany’s policies in the 1930s singling out Jews, including by having them register property. “You tell me,” he said repeatedly, then refused to answer further.

Under fire, Mr. Trump soon backpedaled to suggest that Muslims in the United States might be subject to “surveillance, including a watch list,” rather than a registry. That stance now seems the kernel of policy, judging from remarks by Mr. Trump’s transition team and allies.

In recent days, Kris Kobach, a prominent anti-illegal immigration hard-liner working on Mr. Trump’s transition, said the team was considering whether to formally recommend a national registry for visitors and immigrants from Muslim countries. A day later, Carl Higbie, who was spokesman for a highly visible super PAC behind the Trump campaign, said a registry for Muslims would “pass constitutional muster.” As precedent, he cited the internment of Japanese Americans during World War II — not that he is urging prison camps for Muslims, Mr. Higbie noted comfortingly.

At the least, those incendiary remarks suggest that the transition team hasn’t gotten the memo from Mr. Trump, who has pledged publicly to seek national reconciliation. If the president-elect’s camp is trying to scare the bejeezus out of America’s 3.3 million Muslims, it’s doing a fine job.

Mr. Kobach, the Republican secretary of state in Kansas, suggested that a registry might revive elements of the National Security Entry-Exit Registration System, a measure enacted after the Sept. 11 terrorist attacks that required visitors and immigrants from higher-risk countries, mainly Muslims, to submit to fingerprinting, interrogations and in some cases parole-like check-ins with authorities.

That program was suspended in 2011 under criticism by civil rights groups, which said it stigmatized Muslims. Unlike the internment of Japanese Americans, it did not apply to U.S. citizens, but it certainly affected the relatives of many citizens.

A registry for Muslims, even if masquerading as one for people from “risky” countries,” is no less odious than Newt Gingrich’s proposal this summer, after the terrorist attack in the French city of Nice, to submit all Muslims in the United States to a “test” and deport those who believe in sharia law. Both approaches would screen people based on identity — faith or ethnicity — rather than deeds, and single them out for intrusive and indiscriminate government snooping.

Such a step would be a boon to extremist recruiters and fodder for the Islamic State and other radical groups, which would use it for propaganda purposes as proof of America’s hostility toward Muslims. Equally self-defeating, a religious “test” or registry would risk alienating Muslim citizens of the United States, whose assimilation and loyalty to America are a bulwark against domestic terrorist threats.

In the campaign, Mr. Trump, after dropping his initial proposal for a blanket ban on Muslim immigrants, endorsed what he called “extreme vetting” — specifically, an ideological test to determine whether immigrants are suitable for entry. Rigorous immigration screening is one thing; for the most part, it already takes place. A registry of immigrants is another and would propel the United States into an era of officially induced fear and suspicion.