The students carved up immigration policy into what one of them, Rebecca Chan, described to me as “little fiefdoms”: humanitarian protections, labor laws, immigrant visas, citizenship. Then they performed a kind of public-policy forensics, searching for evidence of new policies in the Federal Register, legal blogs, government Web sites, Listservs for immigration attorneys, and nonprofit newsletters. When they found a change, they logged it in a private database, along with the text of the Obama-era policy that preceded it, and might otherwise be lost. They worked in relative secrecy: some students worried that their database would get hacked by white-supremacist trolls or be co-opted by Trump officials for bragging rights.

Many of the tweaks in the Tracker seem deceptively mundane. Last year, the Administration finalized a rule to nearly double the cost of the naturalization application, from six hundred and forty dollars to a thousand and thirty. (A federal judge in California blocked the rule’s implementation, much as dozens of other changes identified in the Tracker have been enjoined in court.) Guttentag told me, “Literally changing one single word on a form can make a lot of difference.” In January, 2020, the ombudsman for U.S. Citizenship and Immigration Services issued an alert that the agency had begun rejecting certain paperwork if the blank spaces weren’t filled out with the term “N/A,” for “non-applicable.” In December, U.S.C.I.S. redesigned the civics exam given to those applying for citizenship, doubling the number of questions, and giving some answers a conservative bent. The answer to the question “Who does a U.S. Senator represent?” used to be “All people of the state,” but now specifies “Citizens of their state.” All told, new administrative hurdles and other obstacles have cut the number of legal immigrants to the U.S. nearly in half.

By the end of Trump’s Presidency, Guttentag’s Trackers had logged a thousand and fifty-eight changes to the immigration system. Early in the process, he gave me access to the Tracker, and I began to report on the human toll of the lesser-known policies, enlisting a team of postgraduate fellows from the Global Migration Project at Columbia’s Journalism School. In the past few years, we have spoken to two hundred people who bore the brunt of these changes, and found more than sixty cases of irreparable harm that resulted, including torture, sexual assault, and death.