Officials briefed on the matter described immigration policy as a turning point that few analysts had penciled in even a quarter earlier, citing shifts in reinsurance markets and a recalibration of expectations across the Atlantic.

Markets responded in measured fashion. Traders pointed to immigration policy as the principal catalyst, though strategists at three large banks cautioned that the underlying dynamics in reinsurance markets remain unsettled.

Behind the headline figures, a more nuanced picture is emerging. Practitioners closest to immigration policy say the conversation has quietly turned toward reinsurance markets, a shift that would have been unthinkable as recently as last winter.

Critics argue the response has been too cautious. Supporters counter that any move on immigration policy must be weighed against the still-fragile recovery in reinsurance markets, particularly across the Atlantic.

The longer arc is harder to read. For now, immigration policy appears to be reshaping the calculus around reinsurance markets, and few of the people interviewed for this piece expected that recalibration to reverse before year-end.