It’s not exactly a secret that Democrats would love to spend the next several months arguing with Republicans about the future of Social Security and Medicare. Polls show most voters heavily favor the Democratic approach on the social insurance programs, and the GOP often finds itself on the defensive on the issues, which is why it prefers to focus attention elsewhere.

Nevertheless, the Republican Study Committee released a budget plan last week, and as NBC News reported, the group — representing more than three-quarters of the House Republican Conference, including the entirety of the GOP leadership team — endorsed going after Social Security and Medicare, which in turns helped set the stage for a political fight Democrats were, and are, eager to have.

Indeed, it wasn’t long before Democrats started treating the Republican Study Committee agenda like a pinata. As my MSNBC colleague James Downie summarized, “When it comes to Social Security and Medicare, Republicans just can’t help themselves. Even after years of attempted cuts have backfired, they continue to attempt to sabotage the popular entitlement programs — and in doing so sabotage themselves.”

All of this, evidently, gave Donald Trump an idea.

Unfortunately, it wasn’t an especially good idea.

The former president — whose positions on the programs have been largely incoherent and contradictory — published an item to his social media platform late last week, claiming that Democrats are “KILLING SOCIAL SECURITY AND MEDICARE by allowing the INVASION OF THE MIGRANTS.” For good measure, the former president said incumbent President Joe Biden is “killing” the social insurance programs “with the INVASION.”

For now, let’s not dwell on the fact that Republicans really should be more responsible about throwing around reckless words such as “invasion.” Instead, let’s take a moment to highlight the fact that Trump, even now, doesn’t seem to understand how Social Security and Medicare work.

To be sure, I understand the larger political context. Trump is running on an anti-immigrant platform; he realizes that Social Security and Medicare are popular; so he’s eager to connect the dots, telling voters that migrants are undermining the programs.

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But they’re not. That doesn’t make any sense. As a Washington Post fact-check report noted, the presumptive Republican nominee has reality backwards.

Sometimes it’s hard to tell if Trump thinks carefully before wording his social media posts. He wanted to defend his position on Social Security and at the same time knock President Biden for the migrant surge at the border. But 2 2 does not equal 5. Undocumented immigrants improve the health of Social Security and Medicare by paying payroll taxes without receiving benefits.

It’s really not that complicated. When employers hire undocumented workers, many of whom rely on fraudulent Social Security numbers, the businesses subtract payroll taxes that go toward the Social Security and Medicare systems. Those workers, however, will not receive Social Security and Medicare benefits — because they’re ineligible — which means each of those employees is inadvertently strengthening the programs’ finances: They’re putting money into the system without taking anything out.

(Why would they do that? Because even after the payroll taxes are subtracted, these workers believe they’ll make more money than they would in the countries they left behind.)

If Trump were to implement a mass deportation program, and succeeded in removing millions of undocumented workers, that would weaken Social Security’s and Medicare’s finances.

All of which is to say, the question isn’t just whether Republicans will successfully undermine the programs, the question is also why their presidential nominee still doesn’t understand how the programs work.