During his tour of the border town of Nogales, Arizona, Senator John McCain got to play a real-life maverick on the evening news. As part of a delegation of lawmakers working on immigration reform in Washington, McCain witnessed an immigrant scrambling over an 18-foot fence and getting apprehended by border police. The encounter was instantly distilled into a dramatic tweet. The scene, reproduced on the nightly news loop, painted by McCain seemed almost made for television (indeed, some questioned whether the tweet was an elaborately staged stunt). But the Senator was also channeling a primeval refrain in the American psyche.

As the blistery lower lip of the American Dream, the rim of desert connecting the US and Mexico is where the nation’s deepest Hobbesian nightmares are projected daily, with headlines about “aliens” hopping the fence, traversing the desert, being brutalized by smugglers, and all manner of military-style security interventions — from buzzing surveillance drones to traffic checkpoints to border-patrol campaigns with names like “Gate Keeper” and “Hold the Line” (subtly evoking their infamous Eisenhower-era “Operation Wetback”).

The border-as-battleground lives on in the public imagination as a mash-up of the spaghetti western, Cops and CSI. It’s a final frontier, inscribed in the crawlspace between gritty reality and pure fiction: a construct of legal doctrine and geopolitical convention. It’s undergirded by nativist racial anxieties and both steeled and eroded by commercial forces that alternate between craving the free movement of capital and convulsing with fears of labor competition and unbridled markets.