Lesser politicians merely exaggerate or spread fear about what the opposing party would do if they took power in Congress. President Donald Trump is inventing specific pieces of legislation.

Trump’s now rallying supporters by warning them that if Democrats take back the Senate, they’ll pass a bill written by Sen. Dianne Feinstein (D-CA) called the “Open Borders Bill.”

No such bill actually exists.

Here’s what Trump told a rally audience in Topeka, Kansas, on Saturday:

Today’s Democrats have embraced radical socialism and open borders. If you don’t have borders, you don’t have a country, folks, you don’t have a country. Every single Democrat in the US Senate has signed up for the Open Borders — and it’s a bill! It’s called the Open Borders Bill! What’s going on? And it’s written by — guess who — Dianne Feinstein.

Here is the part of Trump’s riff about Democrats that is correct: There is, in fact, a bill that Feinstein has written that every Democrat in the Senate has signed on to.

It is, of course, not called the Open Borders Bill, because it’s not actually about opening the borders at all. It’s called the Keep Families Together Act; it was written in June, during the height of the family separation crisis at the US-Mexico border, to stop the administration’s “zero tolerance” policy of criminally prosecuting parents who crossed into the US illegally and sending their children into the care of the Department of Health and Human Services.

Feinstein’s bill — probably by mistake — would have prevented parents from being arrested for serious crimes by the FBI, not just from getting separated at the border. But the good-faith critiques of the bill snowballed into an assertion on the right that Democrats were going to open the borders — and, furthermore, that that was the point.

How the Keep Families Together Act became the Open Borders Bill

On June 7, Feinstein introduced the Keep Families Together Act. Within days, it had been co-sponsored by every Democrat in the US Senate. The bill went nowhere — Sen. Chuck Grassley (R-IA) made no effort to move it through the Senate Judiciary Committee — and it existed mostly as a foil for Republican proposals to end family separation by allowing the government to keep families in immigration detention indefinitely.

The point of Feinstein’s bill was to end “zero tolerance” by prohibiting agents from separating parents from children, except in cases of abuse or endangerment.

As written, though, it didn’t apply just to Border Patrol officers’ apprehension of families or to the prosecution of parents for misdemeanor immigration violations. Under the bill, no agent of the Department of Homeland Security, the Department of Health and Human Services, or the Department of Justice would be able to separate a parent from children anywhere within 100 miles of a US border.

In other words, as Gabriel Malor pointed out in an article for the Federalist, “The proposed law would apply with equal force to, say, FBI agents (part of DOJ), Secret Service agents (part of DHS), and Centers for Disease Control officers (part of HHS) in the exercise of their everyday duties.”

That includes arresting people for serious crimes, since adults can’t be taken into criminal custody with their children. (This was the whole reason “zero tolerance” led to family separation to begin with). And the 100-mile zone legally defined as the “border” encompasses nearly two-thirds of the US population.

It’s impossible to recognize an accurate critique — that Democrats had (probably accidentally) written a bill that would protect parents from federal arrest in much of the US — in Trump’s attacks on the “Open Borders Bill.” But there was a seed of truth inside a snowballing exaggeration about what the bill would do, and what Democrats’ intention was in drafting it. Here’s a timeline of that evolution:

June 18: Sen. Susan Collins (R-ME), asked about Feinstein’s bill on “Face the Nation,” says that while she appreciates Feinstein’s compassion, “Her legislation is not the answer. It is far too broad. It would essentially prevent arrest within 100 miles of the border, even if the person has committed a serious crime or is suspected of terrorist activity.” Collins’s brief answer didn’t specify that it only applied to parents or that it prevented arrest only where arrest required family separation — in other words, that it didn’t stop immigration agents from apprehending families and detaining them briefly together.

Sen. Susan Collins (R-ME), asked about Feinstein’s bill on “Face the Nation,” says that while she appreciates Feinstein’s compassion, “Her legislation is not the answer. It is far too broad. It would essentially prevent arrest within 100 miles of the border, even if the person has committed a serious crime or is suspected of terrorist activity.” Collins’s brief answer didn’t specify that it only applied to parents or that it prevented arrest only where arrest required family separation — in other words, that it didn’t stop immigration agents from apprehending families and detaining them briefly together. June 19: Malor’s piece is published at the Federalist, with the headline “Democrats’ Border Separation Bill Would Let Nearly All Parents Who Commit Federal Crimes Get Off Scot-Free” — slightly exaggerating the scope of the bill from two-thirds to “nearly all,” and from prohibiting criminal custody to prohibiting any punishment. Malor says the bill could have been “the consequence of extremely careless and hurried drafting,” but could also have been deliberate — in a “monstrous attack on law and order.”

Malor’s piece is published at the Federalist, with the headline “Democrats’ Border Separation Bill Would Let Nearly All Parents Who Commit Federal Crimes Get Off Scot-Free” — slightly exaggerating the scope of the bill from two-thirds to “nearly all,” and from prohibiting criminal custody to prohibiting any punishment. Malor says the bill could have been “the consequence of extremely careless and hurried drafting,” but could also have been deliberate — in a “monstrous attack on law and order.” June 19: Breitbart publishes a blog post that presents Malor’s article and Collins’s statement as two separate critiques of the bill — and says Feinstein’s bill would “effectively prevent authorities from arresting illegal aliens within 100 miles of the U.S. border.” The argument (which appears to be a further interpretation of Collins’s comments) is now in the realm of the definitively untrue. Because family detention facilities do exist (as do procedures for apprehending unauthorized immigrants without lengthy detention), Feinstein’s bill wouldn’t prevent immigration agents from apprehending any unauthorized immigrants.

Breitbart publishes a blog post that presents Malor’s article and Collins’s statement as two separate critiques of the bill — and says Feinstein’s bill would “effectively prevent authorities from arresting illegal aliens within 100 miles of the U.S. border.” The argument (which appears to be a further interpretation of Collins’s comments) is now in the realm of the definitively untrue. Because family detention facilities do exist (as do procedures for apprehending unauthorized immigrants without lengthy detention), Feinstein’s bill wouldn’t prevent immigration agents from apprehending any unauthorized immigrants. June 19: The GOP writes a blog post, “They Should Have Read The Fine Print,” attacking red-state Democrats from signing onto Feinstein’s bill. They, too, quote Collins’s claim that the bill “would essentially prevent arrest,” in addition to pasting the full text of Malor’s article. It doesn’t make any claims about whether the Democrats meant to write such a broad bill.

The GOP writes a blog post, “They Should Have Read The Fine Print,” attacking red-state Democrats from signing onto Feinstein’s bill. They, too, quote Collins’s claim that the bill “would essentially prevent arrest,” in addition to pasting the full text of Malor’s article. It doesn’t make any claims about whether the Democrats meant to write such a broad bill. June 20: The GOP tweets out a link to the blog post, but the text of the tweet goes further than the blog post itself — asserting that the intent of the bill is “open borders.” “The Dem Senators who signed this bill should just be honest with the American people and admit they support an open border policy,” the tweet says.

From there, Trump’s only innovation was to lie about the name of the bill. In doing so, of course, he cemented both the idea that Feinstein’s bill would actually “open the borders” (i.e., prevent apprehension of any unauthorized immigrant entering the US) and the idea that this was intentional.

It fits ever so neatly into Trump’s closing electoral argument, that he and Republicans are the only thing standing between America and mob rule. But thanks to the game of attack-ad telephone, Trump’s claims bear so little resemblance to reality that it almost feels academic to point out their distant ancestor in truth.