Republicans don't fear a backlash on immigration. They should.

Congress has not passed a single bill as unrelentingly hostile to immigrants as the recently approved GOP budget mega-bill in decades, if not a full century. Simultaneously, the new GOP budget bill allocates a breathtaking $170 billion to escalate President Donald Trump’s program of militarized mass deportation aimed at undocumented immigrants and revokes access to much of America’s social safety net for broad categories of legal immigrants.

A new Bloomberg analysis of Census data helps explain why virtually all Congressional Republicans felt comfortable approving so many harsh measures targeting both legal and undocumented immigrants alike: Hardly any of them must fear a direct political backlash from those policies.

Even as the foreign-born share of the US population is approaching a record high, Congressional Republicans have remained almost entirely insulated from the change. Fewer than 1 in 6 House Republicans represent districts where the share of foreign-born residents exceeds the national average, according to the analysis by my Bloomberg Opinion colleague Carolyn Silverman. Likewise, just four of the 53 Republican Senators represent states where the share of foreign-born residents exceeds the national average.

Ironically, the Republican who may be most exposed to an immigrant backlash against these policies is President Donald Trump. Although he cannot legally run again, the coalition he has built at the national level has come to rely on voters who are naturalized immigrants. Republicans will need them in 2028 as demographic change continues to erode the more traditional pillars of their electoral base.

The non-partisan Pew Research Center, in its widely respected Validated Voter analysis, recently found that Trump in the 2024 election improved his performance from 2020 much more among naturalized citizens than among native-born voters. “When you look at all the major groups [of naturalized citizens], people who are college [educated] versus those who are not, men versus women, different racial and ethnic groups, the pattern you see is all of these groups moved more toward Trump in 2024,” said Mark Hugo Lopez, director of Race and Ethnicity Research at Pew.

Overall, the US has experienced a historic growth in the foreign-born share of the population since the passage of the landmark 1965 immigration reform bill. Since then, the foreign-born portion of the US population — which includes both legally present immigrants and those who are undocumented — has steadily increased from about 5% in 1960 to 14.3% in 2023, according to the Census Bureau’s annual American Community Survey. That would put the foreign-born share of the population near the all-time highs of almost 15% in both 1890 and 1910, during the era of mass migration from Europe.

Yet the Republican congressional majorities are overwhelmingly built on the places least touched by that change. In the House, 166 districts contain more residents born abroad than the national average. Republicans hold just 33 of those high-immigration districts, compared to 133 held by Democrats.