Dan Janison Melville. N.Y. Tuesday January 26, 2010. Daniel Janison,

Dan Janison has been a reporter at Newsday since 1997.

At times, the public proclamations of an American president can show an impact regardless of what Congress or the courts allow.

Even with delays in his proposed funding of the big wall and in defunding “sanctuary cities,” President Donald Trump’s presence seems to have boosted deterrence of illegal immigration.

The Department of Homeland Security this month released figures that indicated a stunning 93 percent drop since December of parents and children trying to enter the U.S. illegally from Mexico.

DHS officials told the Reuters news agency that the administration has focused on women with children, which has been the fastest-growing group of undocumented arrivals. In December, 16,000 parents and children were reportedly apprehended. In March, when the numbers usually rise, the total was just over 1,100.

For months, Central Americans heard about Trump’s crackdown polices. Public service announcements directed at them and funded by the U.S., UN and regional governments warned of bleak conditions if they went north, Reuters reported.

An ad in Honduras even featured a mother saying of her daughter: “It’s been a year and I don’t know if she is alive or dead. . . . Curse the day I sent her north.”

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DHS planned to separately detain mothers and children caught at the border. Imposing or threatening this — and other tough policies — was enough to send the numbers downward, officials said.

David Frum, a former Bush administration adviser, wrote in The Atlantic this week: “This spring’s immigration turnabout was unexpected, to put it mildly, by most participants in the immigration debate.

“For years, the predominant view has been that migration flows — legal or not — are powered by deep tidal currents beyond the control of mere human governments,” Frum wrote.

The sharp estimated drop in the number of illegal border crossings apparently accelerates a trend that began years ago.

Back in 2009, after the economy crashed and jobs dried up, a big slowdown in the flow was recorded. But it didn’t end there.

In 2015, The Washington Post interviewed Monica Camacho-Perez, who had come to the U.S. from Mexico as a child 13 years earlier, crossing into Arizona with her mother in the same place her father jumped the border years earlier.

But starting in 2012, she said, her uncle tried to slip into the country and join the family in Baltimore — but was stopped three times by the U.S. Border Patrol and jailed for weeks.

By 2015, authorities were reporting the biggest ebb in illegal immigration in 20 years. Homeland Security officials under presidents Barack Obama and George W. Bush, who poured billions into new border technology, cited enhanced security.

Numbers from the Pew Research Center two years ago indicated that the population of immigrants in the U.S. illegally, which more than tripled to 12 million between 1990 and 2007, had dropped by about 1 million.

Sometimes an expression of intent prods changes, however, whether long- or short term. Trump has yet to get Congress to enact a tax-cut measure, but his vow to slash corporate rates was widely credited in the most recent stock-market jump, which also has its longer-term causes.

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Regarding immigration, it seems logical to expect a debate to further develop between Republicans and Democrats along the lines of what happened with crime in New York City.

It fell sharply, as it did in other cities, following Republican Rudy Giuliani’s successful law-and-order campaign for mayor, accelerating a trend that began under his Democratic predecessor David Dinkins.

Government had already invested heavily in the 1990s in expanded police forces, jail space and other resources.

Some activists went so far in recent years to call Obama the “deporter in chief.”

Whatever the political recap, though, those numbers have evidently plunged early in Trump’s tenure — and supporters are quick to credit him.