Republican presidential front-runner Donald Trump may want to build a giant wall along the U.S.-Mexico border, but it would be Ben Carson who is open to defending it with deadly drones.

While touring the southwest border on Wednesday, Carson — a renowned neurosurgeon running for the Republican presidential nomination — said he would not rule out military drone strikes to keep immigrants from crossing illegally into the United States.

Carson’s comments, first reported by the CBS5 News in Arizona, are just the latest in a series of far-flung options floated by Republican candidates, many of whom in recent weeks have discussed means to decrease the undocumented immigrant population currently in the U.S. and keep others from coming. Proposals have ranged from politically impossible to outrageously expensive, veering the immigration debate far to the right in ways that could seriously imperil the Republican Party when it comes time for the general election.

Trump has played a significant role in pushing the needle, calling on the Mexican government to foot the bill in building a fence across the U.S.-Mexico border. (A spokesman for Mexican President Enrique Pena Nieto assured Bloomberg that scenario simply isn’t happening, while experts contend the plan would cost millions and wouldn’t work). Meanwhile in the last few days, more than half of the GOP field has said they are open to ending birthright citizenship, a political feat that would require changing the United States Constitution.

But the option Carson is leaving on the table — military strikes against likely unarmed and unidentified targets — is clearly profound.

Republicans have long hailed heightened enforcement at the border as a precondition for immigration reforms aimed at addressing the estimated more than 11 million undocumented immigrants currently living in the United States. Lawmakers have flooded the border with resources since the 9/11 terror attacks, flushing the budget with more than $3.7 billion a year and 21,000 Border Patrol agents on the ground. 

Critics of the heightened enforcement presence at the border say militarizing the 1,933-mile stretch better serves to keep undocumented immigrants in the United States, rather than shutting them out. 

Other candidates — former Govs. Rick Perry of Texas and Jeb Bush of Florida, for instance — have said they support surveillance drones to aid agents in pin-pointing border-crossers in real time. But what Carson referred to takes militarizing the border to levels unheard of before. 

The Obama administration has faced backlash for its military drone program to combat terrorism in the Middle East, the details of which are tightly under wraps. But the high-profile deaths of U.S. citizens killed in targeted drone attacks abroad have highlighted the often unintended consequences associated with the lethal machines.

Military drones used domestically would be a chilling policy considering that many of those crossing the border in recent years have been unaccompanied children fleeing extreme violence. But it is emblematic of the fiery rhetoric entering the immigration debate, and the views shared by large swaths of the base that these candidates are vying to attract.

A number of GOP presidential candidates have suggested that Islamic terrorists have infiltrated the United States through the porous border. And just this week, Media Matters reported that well-known conservative radio host Jan Mickelson said that any undocumented immigrant that does not self-deport by a certain time-frame should become “an asset of the state.”

“Well, I think everybody would believe it sounds like slavery?” said one listener who called in to challenge Mickelson.

“Well, what’s wrong with slavery?” he responded.