Donald Trump’s most fervent supporters can do him and the country a massive favor right now: Stop making excuses for his numerous failures to secure the southern border and start threatening to stay home on Election Day 2020 if he doesn’t show more urgency for his main campaign issue.

NBC reported last month that “the Department of Health and Human Services has requested [Department of Defense] support for bed space for up to 5,000 children.” The report added that the Department of Homeland Security is “working on a plan that would allow defense funds and personnel to be used in transporting immigrants in need of medical transport.”

That’s three federal agencies being crushed under the weight of an unabated flow of migrants showing up at our door in need of welfare. Yes, welfare — that’s millions of dollars in healthcare and child services they’re immediately receiving upon arrival, Democrats' denials notwithstanding.

A series of absurd court orders and a Democratic Party that aggressively stands for open borders share the blame for this chaos. But Trump sold himself to the public as the ultimate dealmaker, Mr. “I alone can fix it.”

Trump has tried, but he just gives up when he meets with opposition. His Justice Department began fully implementing punishment for border crossers in 2018 (he caved on that); he backed legislation by Sens. David Perdue, R-Ga., and Tom Cotton, R-Ark., that same year that would have secured the border and implemented a merit-based immigration system (it was never heard of again); and he shut down the government in early 2019 to get more money for a border wall (he caved on that).

The one thing Trump has done right is begin construction of several miles' worth of effective wall barrier along the southern border.

Unfortunately, as I found out when I went to the Texas border in January, no amount of wall can fix the asylum sham that Central Americans are taking full advantage of when they show up at the Rio Grande. One magic word, "asylum," allows them into the United States almost without condition.

But Trump can actually make a difference there. So far, he’s shown no sign that he fully understands the gaping asylum hole or that he cares. But assume for a second that he does, and here’s something he could do that he has so far never been able to do: Make a deal!

Trump can drop the wall, at least for now, and instead propose a trade with Democrats: citizenship for recipients of the Deferred Action for Childhood Arrivals program in exchange for an end to the asylum racket.

Maybe Democrats will reject the offer, but let’s at least see them answer for it. Let’s at least see them get uncomfortable on the issue. Let’s at least see their 2020 presidential candidates explain why the Americans are better off funding free healthcare and child services for hundreds of thousands of non-citizens month after month.

Trump on Sunday effectively fired Kirstjen Nielsen, his secretary of homeland security, because he was dissatisfied with what’s happening to our border. Too bad for her, but it should even be worse for Trump’s 2020 prospects. He can appoint any new secretary he wants, and so long as the asylum law remains unchanged, it won’t make one bit of difference. Whom will he fire then?