Welcome to Secret Identity, our regular column on identity and its role in politics and policy.

The Trump administration’s policy that has resulted in separating children from their parents as part of its border-enforcement strategy is generating widespread opposition, even from people who have traditionally been allies of the president. It has forced the administration to defend an approach that polls terribly and results in images of children in cages and accounts of breastfeeding kids being taken away from their mothers.

It seems like bad politics.

So why do it? The administration’s explanations aren’t much help here. President Trump said he hates the separations and falsely claimed that they’re the product of laws passed by Democrats. Other officials have denied that the policy exists at all. Attorney General Jeff Sessions invoked the Bible to defend the strategy, referring (unwittingly, I assume) to a passage from Romans that people used to defend slavery in the 19th century. And while the implementation and defense of this policy is perhaps the most jarring action the Trump administration has taken so far on immigration, other such policies, like ending the Deferred Action For Childhood Arrivals program, have also been unpopular and defended in misleading ways.

But there is a potential driving force behind many of the administration’s immigration policies, one that it largely avoids discussing in public but that ties all these disparate actions together: reducing or at least stopping a pre-Trump spike in the number of immigrants in America.

I don’t think it’s a secret that immigration policy is an issue that hits on identity, or that Team Trump is not wild about immigrants. But understanding Trump’s immigration policies as a full-scale revolt against rising numbers of foreign-born Americans helps explain what is happening: Controversial immigration policies that would limit both legal and illegal immigration, often combined with rhetoric designed to cast immigrants, usually falsely, as a criminal or national security threat.

America is in the midst of an immigrant boom, by historical standards. The U.S. Census Bureau estimates that 14 percent of Americans, about 44 million people, are foreign-born. Those numbers are up from 2000, when about 11 percent of the population (31 million Americans) were foreign-born. The foreign-born population had hit almost 15 percent at its peak around 1890, but it dipped below 5 percent by the 1970s. So it is quite high now (compared to the past 50 years), and the Census Bureau estimates it will hit 15 percent again over the next decade.

If you think of stopping the growth in the foreign-born population as the unifying goal — rather than strengthening national security or promoting law enforcement — then Trump’s immigration agenda hangs together more clearly. The steps taken or proposed by the administration, such as ending DACA and sharply curtailing refugee admissions, are likely to result in: some foreign-born people currently in the U.S. being forced to return to their home countries, including highly skilled tech workers; those who remain here having a harder time helping relatives come to the country; fewer refugees ever entering in the first place; and some immigrants who got citizenship having it revoked.

Reducing the nation’s foreign-born population is also an issue the president’s allies talked about before they entered the government.

“It’s important to understand that historically speaking, that immigration is supposed to be interrupted with periods of assimilation and integration,” senior Trump adviser Stephen Miller said in a radio interview in 2016, according to Vox.

“We should follow America’s history, and the history of America is that an immigration-on period is followed by an immigration-off period,” he added.

The Center for Immigration Studies — a D.C.-based think tank that describes itself as “low-immigration, pro-immigrant” and has close ties to the Trump administration — and Attorney General Jeff Sessions have also long lamented the growth in the immigrant population overall.

And most Republican voters want less immigration. According to Gallup, most Republicans want the number of immigrants to go down, while Democrats are both less concerned about immigration overall and increasingly opposed to reducing the number of immigrants. Almost 80 percent of Democrats think immigrants strengthen the country, according to a 2016 Pew Research Center poll, compared to about a third of Republicans.

So why doesn’t Team Trump just say that it wants to limit the foreign-born population? Well, some members do, particularly Miller. But I suspect that you don’t hear that sort of justification more often because focusing on the raw number of immigrants would be viewed as racist. And it might be racist. The majority of immigrants in the U.S. today are from Asia and Latin America.

I simply don’t know if Miller or Sessions would be as concerned about an immigration boom if the people entering the U.S. were British, French or German. Trump reportedly suggested he would like more immigrants from Norway, a heavily white nation. So that’s a clue. And a 2016 poll from the Public Religion Research Institute and the Brookings Institution showed that a majority of Republicans thought immigration levels were too high for people from Central America and Mexico, the Middle East, and predominantly Muslim nations, but less than half of Republicans felt that way about Asia (despite high immigration levels from that region in recent years), Africa, Europe or mostly Christian areas.

In any case, not talking about the true roots of the administration’s immigration policy has costs. Some of those costs were clear when Sessions cited Romans to suggest that separating kids from their parents was supported by the Bible. Unable to say, “We want fewer foreign-born Americans, full stop,” the Trump administration is instead constantly making arguments that don’t withstand much scrutiny. White House chief of staff John Kelly suggested last month that recent immigrants are struggling to “assimilate” into U.S. society. A 2015 study, however, found that new immigrants are learning English and taking other steps to integrate into American culture just as quickly as past generations of immigrants did. But does Kelly really think new immigrants coming to the U.S. can’t assimilate, or does he oppose additional immigrants coming to the country and think that talking about assimilation is a more politically palatable way to defend this position?

The other problem with not having a debate about what really seems to be driving the administration’s immigration policies is that we don’t know whether Democrats (at least Democratic elites) are comfortable with growth in the foreign-born population and what, if any, new immigration limits they would back. Do they support the gradual increase in the number of immigrants that the Census Bureau projects we will see? Would they support a larger increase? Do they view the future U.S. as a more racially mixed place with no one group forming a majority — like California — or as a majority-white nation? How do they want immigration policy enforced, and should that change dramatically from now on, as some activists in the party call for the abolition of the federal Immigration and Customs Enforcement agency?

I doubt this debate over the foreign-born population will emerge publicly and directly. It’s a bit challenging for both sides — particularly the Republicans. But it would be ideal if we had an argument over what we are actually arguing about, instead of having Trump make misleading claims about immigration, which fact-checkers then criticize, while the president avoids mentioning the values and goals that I think are actually undergirding the administration’s immigration policies.

What else you should read

I can’t think of anyone who follows the day-to-day details of Trump’s immigration policy better than Vox’s Dara Lind does. She is particularly good at explaining exactly how Trump’s policies differ from those of former President Barack Obama (whose administration deported more than 2 million people) and when they actually aren’t all that different. Follow her on Twitter ( @DLind). She is one of my must-reads.

One more person to follow. Trump’s policy on separating children from parents is generating strong opposition across the religious community (leaders of Catholic, evangelical Christian, Jewish and Muslim organizations are among the critics), and Religion News Service’s Jack Jenkins (@jackmjenkins) is covering that story closely. And he’s great overall on the intersection of religion and politics.

California Sunday interviewed a variety of people in (from high school teachers to leaders at venture capital firms) about the under-representation of people of color and women in the tech industry. This is a very familiar issue for the tech industry (and many others), but this range of perspectives was unique.

This new data about Harvard’s admissions policies and how they appear to negatively affect Asian-Americans was compelling and is likely to lead to sharp criticism of the university.

By the numbers

Up to 50,000 people each week attend services at Houston’s Lakewood Church, according to a Houston Chronicle article. And unlike many American Christian churches, which are typically still dominated by one racial group or another, Lakewood (which is non-denominational) has substantial blocs of Asian, black, Latino and white congregants. Lakewood’s services are also broadcast nationally, drawing an estimated 10 million viewers each week. That reach — in Houston and nationally — has made Lakewood’s lead pastor, Joel Osteen, an influential figure in American Christianity. But Osteen is also controversial — because of another figure mentioned in that Chronicle story: $12 million, the value of the home Osteen lives in, according to the article. His critics view Osteen as a symbol of a vein of American Christianity too focused on material wealth. It’s worth checking out the Chronicle’s recent three-part series on Osteen and Lakewood.

If you have ideas for this column, you can reach me via e-mail (perry.bacon@fivethirtyeight.com) or Twitter (@perrybaconjr).