But Trump presented the same fix for the crisis as for every other problem in his speech: the border wall that he’d gone on TV to pitch. The epidemic, in that way, was only a convenient means to an end, fuel for an argument the president has been making for years. The wall is the only proposal that Trump has genuinely fought to enact as president, but it’s the one that will almost surely do the least to halt the epidemic.

The Trump administration has already admitted as much. A 2018 assessment from the Drug Enforcement Administration noted that most of the heroin flowing into the country comes through “legal ports of entry, followed by tractor-trailers, where the heroin is co-mingled with legal goods.” Only a “small percentage” comes through areas of the border between ports of entry—the places a border wall could theoretically cover. When it comes to fentanyl, the other major driver of the opioid epidemic, the DEA says it’s not certain that Mexico is the main front, though large quantities of the drug are seized at the border. Fentanyl can be ordered through the mail from China, and it is typically much purer, and thus more potent and deadly, than Mexican-sourced fentanyl.

Read: It’s too soon to celebrate the end of the opioid epidemic

The DEA’s conclusions make sense: Opioids are a big business. Their production is industrialized and sophisticated. Sending ad hoc groups over the border with fentanyl and heroin, in the no-man’s-land between ports of entry, is likely not efficient enough to meet intense American demand. No wall could help stop the flow, in other words, no matter how well it’s funded and no matter what it’s made with.

The White House knows that. Yet, as on Tuesday, the occasions when Trump has mentioned the opioid crisis have usually been connected to the wall. In a major anti-opioid campaign announced last year, he falsely blamed undocumented immigration and so-called sanctuary cities for sparking the epidemic. Even in October 2017, when the president declared a national public-health emergency to confront opioids head on, the wall was part of his argument. Though he proposed measures championed by the public-health community—such as tightening prescription guidelines and qualifications, and helping states with substance-abuse programs—his standard bluster on the wall and immigration followed quickly behind. “For too long, dangerous criminal cartels have been allowed to infiltrate and spread throughout our nation,” Trump said during that declaration. “An astonishing 90 percent comes from across the border, [for] which we are building a wall which will help in this problem.”

According to federal reports, even Trump’s public-health emergency hasn’t amounted to much. A Government Accountability Office audit of the response found that the Department of Health and Human Services activated just three of the 14 authorities made available by the declaration. While those three measures have accelerated substance-use treatment and research and have promoted medication-assisted treatment—all items recommended by a federal opioids commission—they amount to minor bureaucratic tinkering in the face of a titanic problem. In all, between White House initiatives and Republican-passed legislation over the past few years, the federal response to opioids has acted mostly on the margins. The most recent moves have involved legislation to make it more difficult to ship fentanyl by mail. But there is no massive mobilization.