President Trump is once again demanding his wall, apparently undeterred in his quest to worsen America’s immigration problems. In this pursuit, Trump has stumbled through a series of dreadful policy choices.

First, he instituted a hastily crafted and illegal ban on Muslims. Then he rescinded the Deferred Action program for Dreamers. Now, he has returned to his original bad idea, “build the wall,” at the expense of proven methods to defend the border and sacrificing American moral authority. It’s another example of a Trump two-fer: policy that doesn’t work and takes the shine off the American star. Chuck Schumer and Senate Democrats are right to object to the wall, for there are far better ways to secure our border.

Over the last few weeks, Trump has vacillated over various immigration proposals. It remains to be seen what his ultimate plan will be (if he has one), but for now, we know he wants to trade the lives and status of 800,000 Dreamers — young people brought to this country as children, with strong academic achievements or honorable service in the U.S. military and no criminal record — for his wall.

Thus, he is willing to resuscitate a program that actually worked, but which he sabotaged, in exchange for satisfying his infantile obsession with a great, big, beautiful wall. And while the federal court system has temporarily put a stop to Trump’s use of the Dreamers as pawns, there is no doubt that he will still fight to get his wall.

Simply put, the wall is bad policy. Trump believes it will stem the drug trade and illegal immigration — but walls are easily circumvented. Most of the drugs brought into the United States do not come across areas where Trump would build his wall; instead, they come through legal ports of entry. Drug smugglers have calculated that it is easier to sneak drugs through populated areas in major ports than it is to haul them across empty but unforgiving landscapes. And even where border walls currently exist in metro areas, the cartels tunnel underneath or find other ways around. A wall built through sparsely populated land will be easy to avoid.

Nor is the wall likely to halt illegal immigration, which has been declining over the last decade (long predating Trump). Most illegal immigrants coming to this country bypass the hard way in: They do not make the long, dangerous trek across empty deserts where Trump’s unwelcoming wall would loom. Instead, they do it the easy way: They arrive in the United States on a legally obtained visa, and then overstay the visa. A border wall does literally nothing to solve this problem.

Moreover, building the wall would likely cost more than $18 billion over the next 10 years — more than half of the $33 billion that is likely to be spent on border security over the next decade. Apparently, Mexico has not agreed to foot the bill.

It goes without saying that the Department of Homeland Security (where I served under the Obama administration) could better allocate that money to keep our borders safe. Indeed, the White House is reportedly asking DHS to make cuts to existing border security priorities in order to fund the wall — including infrared cameras that allow Border Patrol agents to track smugglers and illegal migrants; surveillance aircraft that allow DHS to track narcotic routes far from our borders; coastal interceptor boats that protect our shores; and canine units that sniff out drugs and bombs at airports and other ports of entry.

Perhaps worst of all, the proposal would also cut the number of new customs officers — the very people we rely on to keep our borders safe.

The wall is a bad idea. It will not do what Trump says, and it will cut workable security programs. But the wall also has a more pernicious effect. America has long been the land of opportunity for new immigrants, who have come here seeking better lives. These men and women have improved this country by their work ethic and enriched the American cultural fabric. It is this soft, cultural power that has undergirded American leadership for the past century.

But the wall tells the rest of the world: Stay Out. We don’t want you here. America’s walls are going up, and the rest of you can fend for yourselves. You can’t rely on American leadership anymore.

And so Trump’s wall will drag America further down the path of global pariah on which Trump has set it, sliding inexorably toward irrelevance. It is time to reverse that slide — and one place to start is by rejecting Trump’s wall.