According to statistics from Immigrations and Customs Enforcement, the number of Mexican citizens deported from the United States in the first three months of 2017 dropped by nearly 20 percent from a year earlier.

The Mexican government’s statistics also show a slowdown in Mexican citizens being kicked out of the United States during January and February, with fewer deportations in those months than during any month last year. (March figures were not yet available.)

The number of deportations often fluctuates considerably from month to month, for a variety of reasons, and an official with the American immigration enforcement agency cautioned against drawing any firm conclusions from the recent decline.

But whatever the pace of deportations under Mr. Trump turns out to be, he has already provoked a nationalist surge in Mexico, uniting the country across political and economic divides in outrage at his stance on immigration, trade and border security.

Carlos Bravo, a historian at CIDE, a Mexico City university, said Mexican politicians were clearly trying to respond to — and perhaps gain from — that popular anger. Rallying to the side of Mexicans kicked out of the United States offers them an easy way to score points at home, with few political risks.

The cause of deportees “has very few costs,” he said. “It’s a noble cause” in the eyes of most Mexicans.