Mitt Romney speaks to supporters at a February rally in Mesa, Arizona. Photo: Flickr/Gage Skidmore

Mitt Romney wants a border fence. But he doesn’t just want to finish the physical fence that’s already there in bits and pieces. He wants a high-tech fence: you remember, the one that was tried, wasted a billion dollars, and didn’t work.

“As I have said many times, it is critical that we redouble our efforts to secure the borders,” Romney said to the National Association of Latino Elected and Appointed Officials on Thursday. “That means both preventing illegal border crossings and making it harder to illegally overstay a visa. We should field enough border patrol agents, complete a high-tech fence, and implement an improved exit verification system.”

What he’s really talking about are two high-tech border fence plans, one which utterly failed — SBInet — and its successor, which is merely problem-prone. SBInet, which aimed to blanket the border with an integrated network of fixed sensor towers spread across hundreds of miles, should have allowed Border Patrol agents to track crossings from anywhere. But unanticipated delays and problems with using fixed towers in remote and hilly terrain caused the sensors to break down in the weather or be rendered useless by interference.

The mere 53 miles of SBInet built in Arizona also came at a price tag of $1 billion. That left 334 miles uncovered in Arizona alone out of a nearly 2,000-mile border, which meant the costs for a complete (and impractical) high-tech fence could have been astronomical.

The program was dumped. But DHS never really gave up on the idea of a virtual border shield. SBInet’s present-day successor in the Arizona Border Surveillance Technology Plan, is intended as a cheaper, more slimmed-down and mobile high-tech “fence.” It’s implementation is limited to just Arizona, for now. And it relies less on towers — though it still plans to deploy them — and more on drones and truck-mounted mobile radars that can move around obstructing terrain.

However, the mobile plan has encountered a similar set of problems to the ones that crippled SBInet, according to a Government Accountability Office audit released in November. For one, no one knows how much the fence plan will eventually cost — the current $1.5 billion price tag is more like a placeholder — or whether the fence will really work.  The Border Patrol never built in any financial slack for delays in scheduling or for equipment being lost or breaking down (in the harsh badlands of southern Arizona, at that.) Nor does anyone know if the fence will actually reduce undocumented crossings.

You also wouldn’t know it listening to Romney, but new migration to the United States is at net zero. That means as many immigrants leave the U.S. as those who enter. But Romney still says he will “put in place my own long-term solution that will replace and supersede the President’s temporary measure,” Romney said.

It’s strange, because Romney’s other positions vis-a-vis immigration sound like moderate reforms, if a bit vague. During the speech, Romney said he would “upgrade our temporary worker visa program” and endorsed expanding green cards to immigrant families and college graduates. Romney also wants to give a boost to the Border Patrol. He may want to send more pilots, as the Border Patrol does not have enough to fly its new drones.

That’s fine. The main problem with Romney’s immigration platform is that there’s a border fence boondoggle as its centerpiece.