“Open borders” is now not merely a “right-wing talking point.”

The Homeland Security secretary under President Barack Obama says the proposals being pushed by his party’s 2020 presidential contenders are essentially that.

During last week’s Democratic presidential debate, candidate Julian Castro pushed a proposal to make crossing U.S. borders without permission no longer a crime, a position most of the other Democrats onstage promptly adopted. Sen. Cory A. Booker of New Jersey this week vowed that he would issue as president an executive order that would “virtually eliminate immigration detention.”

Former DHS Chief Jeh Johnson though told The Washington Post that these proposals would effectively implement an “open borders” policy.

“That is tantamount to declaring publicly that we have open borders,” he said. “That is unworkable, unwise and does not have the support of a majority of American people or the Congress.”

Mr. Johnson used a phrase that Democrats routinely dismiss as GOP scaremongering.

Mr. Castro himself, when asked Sunday on ABC’s “This Week” program about whether he advocated “open borders,” denied the premise, calling the term “just a right-wing talking point. It always has been.”

The Obama-era DHS secretary also warned that if the next U.S. president implements a de facto open borders policy, there will come a much larger flood of immigrants and asylum-seekers than even the one currently overwhelming border detention facilities.

“If we had such a policy, instead of 100,000 apprehensions a month, it will be multiples of that,” Mr. Johnson told The Post.