The last thing the left wants prior to the midterms is an image dramatizing the weakness of our southern border.

So the caravan of thousands of migrants, emanating from Honduras and headed toward the United States, is considered an illegitimate story, a shoddy excuse for President Donald Trump’s fearmongering.

It’s certainly true that Trump and his allies have thrown up a lot of chaff around the caravan. It’s not being paid for by George Soros, or infiltrated by unknown Middle Easterners. But the president gets the big point right: We have borders, and should enforce them.

Whatever Trump’s exaggerations, the caravan itself isn’t a fabrication. It started as a group of 160 people in Honduras. It quickly grew to 1,600. Guatemala tried to close its border to the migrants, but rapidly gave in. The caravan grew to as large as 7,000 as it crossed into Mexico before shedding people in recent days.

The media has run with the story because it isn’t every day that a group of thousands of migrants crashes through a Mexican border crossing. The images, of a throng of migrants as far as the eye can see on the roads, are compelling. To which the response of progressive commentators has been: No fair.

There have been complaints that The New York Times had front-page photos of the caravan two days running. Then there’s the footage on TV. “Make no mistake,” Bill Maher says, “the TV media is helping Trump and his enablers win the upcoming election.”

This is all misbegotten. Rather than urging that the media ignore the caravan, Democrats would be better advised to lessen their vulnerability on immigration by not treating concerns over border security as inherently fake or hateful.

How hard would it be to say that the caravan should disperse and legitimate asylum-seekers try to get protection in Mexico, long before they reach the U.S. border?

Asked about Trump’s tone on the caravan, Sen. Kamala Harris made it sound as though it’d be un-American to turn the migrants away: “We are a country that — our strength has always been that we are a tolerant country, that we are welcoming, in particular, to those who have fled harm.”

Another typical response is to tsk-tsk worries about the border by citing a decline in illegal border crossings since the 2000s. But this misses the point: Our laws and rules have conspired to render the southern border almost null and void for the category of migration that has been growing at the most rapid clip, families and minors from Central America.

What migrants in the caravan understand is that, as members of a family unit from Central America, if they set foot in the United States, they have a good chance of staying (hundreds of migrants from a 1,500-strong caravan earlier this year reportedly made it into the United States). They can surrender to border agents and probably get a bus ticket to the interior, pending proceedings for which they may never show up.

This is an enormous incentive to make the trek. The caravan is dramatic, but it isn’t different in kind from the daily reality on the border of Central American minors and members of family units showing up and getting in.

Trump is correct that this is an insane way for a sovereign country to run its immigration policy, and that Republicans want to try to fix it by tightening the rules, while Democrats support the latitudinarian status quo.

If Trump’s opponents don’t want to see more caravans on TV, they could agree that the border shouldn’t be arbitrarily open to a swath of migrants from Central America and help do something about it. Instead, they cry foul when Trump points out obvious deficiencies in the current system and hope news organizations don’t notice a group of thousands of people heading north to try to take advantage of our laxity.

Rich Lowry is a syndicated columnist. He can be reached via e-mail at: comments.lowry@nationalreview.com.