(Susan Walsh/AP)
Opinion writer

U.S. border agents fired tear gas into crowds of asylum-seeking migrants at the southern border Sunday, and you can be certain that President Trump will amplify the claim that this turmoil strengthens his case for getting his way on immigration.

He will be aided in this by one of the worst conventions in political reporting — the habit of asserting that a given occurrence “provides fodder” for a politician’s attacks or arguments, simply by virtue of the fact that the politician will try to use it that way, regardless of whether facts or logic support it. For example, the New York Times claims “the unrest” will “likely provide him with additional ammunition” to keep out the migrants.

So let’s be clear on the real meaning of the latest mayhem: It doesn’t give Trump “ammunition” at all. Instead, it shows that Trump’s immigration agenda is a total and abject failure — and that he is covering up this glaring reality with lies.

In a series of tweets, Trump lashed out over the latest border clash. He blamed it on the fact that his administration has stopped separating families, claiming this now means “vast numbers of additional people storm the Border.” He raged that the migrants are “stone cold criminals” and that the Obama administration used the same family separation policy. He vowed to close the border entirely if Mexico does not ship the migrants back home, insisted that Democrats “created this problem” and once again demanded that Congress “fund the WALL!”

Trump is making a real argument, but it’s nonsense

It’s important to understand that Trump is making a real argument of sorts here. To simplify, his basic claim is that Democrats and/or Congress will not change the law in a way that would allow Trump to detain asylum-seeking families all together for extended periods, which means the administration must choose between separating children or ultimately releasing parents pending their hearing.

Trump had to drop the separations due to the political and legal backlash. He’s now saying that means he’ll have to release the parents, and that this will help adults game the system by disappearing into the interior — what he calls “catch and release” — thus encouraging more asylum-seekers to come. In short, Trump blames the current crisis on being hamstrung in one way or another from deterring them with cruel and inhumane policies — he can’t separate the kids, and he can’t detain families indefinitely.

But this whole argument is based on a lie. We already know that cruelty as deterrence doesn’t actually work — and we know this because Trump’s own effort to do this failed.

Vox’s Dara Lind examined the data and found that even during the period of family separations, there was “no evidence” that this “harsh treatment … actually works as a deterrent.” Careful reporting explains why: Asylum seekers from Central America are driven by horrific economic, political and civil conditions at home, so they’re willing to risk the worst to escape it.

The whole premise of Trump’s approach to the migrant crisis — that the answer is ever-escalating deterrence, which is supposed to showcase his “toughness” — has already been revealed as a failure. Indeed, as BuzzFeed points out, the administration has also done other things to try to dissuade migrants, such as eliminate fear of gang violence as a criterion for asylum, yet they keep coming. Trump’s decision to send troops to the border — in addition to using the military as a prop in the GOP’s failed midterm propaganda message — can also be seen as an attempt at deterrence (remember when Trump suggested migrants might be shot?), one that also failed.

Trump is trying to mask this epic failure with other lies. The suggestion that the failure to build the wall is to blame — and that funding it would stop this situation — is absurd, since asylum seekers want to turn themselves in at the border so their claims can be heard. The whole narrative of a “catch and release” criminal menace is itself based on lies and wild exaggerations. Trump’s rage tweet about “stone cold criminals” echoes previous similar claims that have been roundly debunked. And migrants and asylum seekers actually show up for immigration court proceedings at far greater rates than he claims. Meanwhile, Trump is trying to mask the cruelty of his deterrence approach before domestic audiences by claiming his predecessor did the same thing, which is false (though the Obama administration did experiment with forms of deterrence, disastrously).

Trump’s agenda is failing in another way: Other prescriptions he still hopes to implement are deeply misguided and are all-but-certain non-starters. Trump hopes to restart family separations, but some officials remain worried about the blowback — since it would just revive the cruelty in another form — and it’s not even clear it would be legal. Trump just tried to ban asylum-seeking by people who don’t cross at an official port of entry — a cruelly contrived way of restricting people from exercising their legal right to apply for asylum here — but this has been blocked in court. Trump’s threat to close down the whole border — which appears to mean restricting all asylum-seeking, even at official ports of entry — would be a humanitarian and diplomatic disaster, and also likely would not survive legal challenge.

Fox News thinks the border clash helps Trump. It doesn’t.

There is no way what happened Sunday gives Trump “ammunition” to argue for any of those things. The border patrol claims it used tear gas only after migrants threw things at them, but at the same time, tear gas was used on groups that included children. The resulting horrifying imagery only underscores the deep disconnect between the root causes of the crisis and Trump’s “solutions” to it, which only highlights that the crisis remains intractable in the face of Trump’s fabled toughness.

Indeed, the specifics of this event cannot change the underlying reality that the prescriptions Trump now wants would either produce all kinds of unacceptable outcomes or are unlikely to stand up in court, or both. This is an extremely complicated problem, one that bedeviled the Obama administration as well, and one that can probably be addressed only by regional solutions of some kind that seriously grapple with both its complex causes and the need to treat migrants humanely. But Trump’s unstable bluster and threats only make that harder.

Fox News, however, appears convinced that all this imagery helps Trump. As Matthew Gertz of Media Matters shows, Fox has been plastered with coverage of the clash. But that doesn’t mean the rest of us have to pretend it boosts Trump’s arguments. The exact opposite is true.

Read more:

George P. Shultz and Pedro Aspe: How we can help the migrant caravan

The Post’s View: Send judges, not troops, to the border

Rick Barton: This is what Trump should do about the migrant caravan

Dana Milbank: All the reasons the migrant caravan is totally a national emergency

Greg Sargent: Another judge just blocked Trump. His ruling contains a warning.