Arizona Sens. John McCain and Jeff Flake have been longtime advocates for Operation Streamline, the assembly-line criminal prosecution of border crossers en masse. Both introduced S. 744, a bill that proposed tripling the size of Operation Streamline in the Tucson sector.

Flake recently claimed that there is almost “universal agreement” that Streamline reduced unauthorized border crossings in the Yuma sector. He later challenged future U.S. Attorney General Loretta Lynch about the program: “So when we have programs like this that work and we see success in one sector — and everybody can point to that — it’s very disturbing when DOJ (Department of Justice) pulls back on that.”

Apparently, this “everybody” does not include the U.S. Department of Homeland Security’s own Office of Inspector General. On May 15, 2015, OIG released a report showing that Border Patrol does not know if Streamline really deters repeated border crossing, that Border Patrol has no idea what Streamline costs U.S. taxpayers, and that Border Patrol may be violating international treaties by subjecting refugees to prosecution.

Despite the critique from the Inspector General, Operation Streamline does show remarkable effectiveness — at expanding the wealth of private prisons. Corrections Corporation of America, a nationwide corporation running three immigrant “detention centers” in Arizona with federal taxpayer dollars, took in $1.6 billion in 2014 revenue, including $724.2 million from federal government contracts alone. All while turning a tidy profit of $195 million.

McCain has benefited from the private-prison success himself. Through the second quarter of 2014, Sen. McCain had received at least $32,396 in CCA campaign donations.

It is wrong to allow financial windfalls for the private prison industry to drive unsubstantiated border policies.

Sens. McCain and Flake should cease championing Operation Streamline, an expensive program with true costs and impacts that remain unknown.

Leslie A. Carlson is a program evaluation consultant. David R. Wolf is an attorney. Both are members of the End Streamline Coalition.