It should be obvious to everyone by now that Donald Trump's presidency has been a failure on immigration policy.

This is true no matter where you stand on the issue. If you think the United States should be more welcoming to immigrants, then Trump's actions — the Muslim ban, the separation of children from parents, the disruption of communities where immigrants had established themselves — have been a moral disaster. If you're more anti-immigration, you can't be happy, either: Despite the president's most extreme efforts, more migrants keep showing up at the U.S. border every day.

It's been a bad two years. And it's about to get worse.

Kirstjen Nielsen, the homeland security secretary, resigned abruptly on Sunday. More than any official aside from senior adviser Stephen Miller, Nielsen has been the face of Trump's benighted war on immigration. Her departure from office does not mean the president has sensibly reconsidered his approach. Instead, it seems likely he's about to double down, implementing increasingly cruel policies in the name of "toughness."

We got some insight into the president's mindset late last week, when the administration suddenly pulled the nomination of Ron Vitiello to lead U.S. Immigration and Customs Enforcement.

"We're going in a little different direction," Trump said. "Ron's a good man but we're going in a tougher direction. We want to go in a tougher direction."

Appearing tough is in keeping with Trump's public character. But it's a fool's errand.

By any measure, U.S. immigration policy in recent years has been extraordinarily tough. The Obama administration conducted deportations at record-breaking levels — more than all the presidents of the 20th century combined — thinking, wrongly, that such efforts might lead to a compromise with hawkish Republicans on an immigration reform package.

Instead, Trump got elected. Certainly "toughness" hasn't been lacking in his approach to U.S. immigration policy. But people who kneel at the altar of toughness are just like blind followers of any ideology in believing that it cannot fail, it can only be failed. They believe the best possible response to a failure of toughness is more toughness.

The phenomenon is most amply demonstrated in U.S. policy toward Cuba, where sanctions have failed for the better part of a century to dislodge the Communist government — and where Trump, not coincidentally, has been retracting his predecessor's efforts to finally start building relationships.

This same mindset is now at work on the U.S. border. But it will be ineffective there, because no matter how stringent Americans have become, migrants are usually fleeing something worse. As I've pointed out, the Central American immigrants moving north are trying to escape poverty and violence — much of it exacerbated by U.S. policies. And as my colleague Ryan Cooper explained, climate change will likely accelerate those trends.

Addressing those underlying issues will require the U.S. to get smart, not tough.

Toughness is tempting, but over time it often becomes immoral. In this case, America's policies would have to be scarier and deadlier than the poverty and violence migrants are fleeing. That means compounding the suffering of people who are already suffering so much they're willing to travel thousands of miles in search of something better for their families. Getting tougher means, in the end, creating more pain for people who don't deserve it.

There are, of course, Americans ready to go all-in on such harsh policies. The anti-immigration Center for Immigration Studies lauds efforts in Hungary, where police have used tear gas and electrified fencing to keep migrants from entering from Bosnia. Anti-immigrant activist Kris Kobach wants to end remittances to Mexico, preferring to impoverish families across the border to reduce migrant levels here.

Nielsen, for all her flaws, seemed to have some guiding moral principals: She reportedly angered the president by saying his proposals to slow migration were against U.S. law. Now that she's gone, it seems likely the president will search for somebody more amenable to replace her.

The president's policies — the policies Nielsen implemented — have been cruel and ineffective. They could also get much worse. Nielsen's resignation, as terrible as her tenure was, may also be a terrifying turning point.