Attempted border crossings surged in March

It will take a few months to determine if the spike turns into a full-blown surge similar to a migrant crisis that occurred in 2014, but the increase marked a turn for the administration, which a year ago was touting historically low numbers as the "Trump effect" and is now using the statistics as the reason it needs aggressive new immigration enforcement authorities.

The number of people either caught trying to cross the southern border or rejected for admission increased 37% from February into March, a sudden rise in figures that had been holding relatively steady. The increase was driven especially by a jump in the number of people apprehended trying to cross illegally. The number of families and unaccompanied children trying to come into the US increased at a higher rate than the general population.

Last month's numbers were three times those of March 2017, when crossings were at their lowest in two decades of records.

That year also defied the usual trend in March, when crossings historically increase as weather improves. In 2013 and 2014, a summer surge of migrants, and especially child migrants, caused a crisis of overcrowding at detention centers and humanitarian concerns. The March uptick lagged those years by several thousand, and numbers in April and May will be key to determining whether the increase marks a trend or a one-off development.

A senior administration official had told reporters on a call Wednesday announcing Trump's move to send National Guard troops to the border that the numbers were up substantially, using them as a data point in what the President called a "crisis" at the southern border in his memo authorizing troops to be deployed. The monthly numbers were released that evening, slightly ahead of schedule.

Standing at the White House podium Wednesday afternoon, Homeland Security Secretary Kirstjen Nielsen noted the historic drop in border crossings that happened in the first few months when Trump took office, calling it the "Trump effect" and touting the work the administration had done on immigration since.

But the numbers by fall had caught up with levels in the last several years under the Obama administration, and Nielsen cited the same statistics Wednesday that the department once cited as proof of its success as the reason more steps were necessary.

"When the President took office, the traffickers, smugglers, TCOs and the illegal aliens that serve as their currency paused to see what our border enforcement efforts would look like and if we could follow through on the deportation and removal," Nielsen said. "While we have been apprehending aliens at the border with historic efficiency, these illicit smuggling groups saw that our ability to actually remove those who come here illegally did not keep pace. They saw that there were loopholes they could exploit."

Illegal migration is driven by a number of elements, including what are known as push and pull factors. The administration has been aggressively targeting what it says are pull factors: perceptions that they argue attract immigrants to the US because they believe they will be able to stay. It has discussed the push factors less often, however: the violent and impoverished conditions in Central America that send migrants north out of desperation.