That view is shared by the vast majority of Democrats in the country -- and even some of the Republicans running against Trump for president. At the debate on Saturday night, both Jeb Bush and Ted Cruz suggested that the practice remain banned or used very, very sparingly. (Cruz, for what it's worth, said he didn't believe that waterboarding was torture.)
Not only does Trump support the return of waterboarding in the interview with Stephanopoulos, but he seems to suggest that he'd be in favor of a lot more harsh interrogation tactics than that. That's an echo of a sentiment Trump expressed during the conversation about waterboarding during Saturday's debate. "I would bring back waterboarding and I'd bring back a hell of a lot worse than waterboarding," Trump promised.
Trump leaves open the possibility of beheadings -- or at least the specter of the possibility -- in the interview with Stephanopoulos, a pose broadly in keeping with his general foreign policy view that might makes right or that, at the very least, you have to be willing to do anything to anyone to ensure they don't mess with you. You may not actually have to do it. But you have to make sure the enemy knows you are willing to do it.
While there's been very little recent polling of Americans on their views of interrogation tactics or torture methods that go beyond waterboarding, there is some data that suggests that Trump's harder-than-hard-line views on the topic might find some fertile soil among Republican voters.
In a comprehensive 2014 Washington Post-ABC News poll aimed at understanding Americans' views on the use of waterboarding and other "enhanced interrogation tactics," nearly six in 10 said they supported the CIA's methods in interrogating suspected terrorists. The group most likely to see waterboarding as justified? Conservative Republicans.
So, yes, Republicans are more likely to be supportive of using techniques like waterboarding than the rest of the public. And, also yes, they are more likely to think it yields information that couldn't be obtained otherwise.
But, Trump raising the beheadings conducted "in Medieval times" entirely unbidden and making clear that waterboarding would be the least dicey methods he would be okay with suggest a willingness to push the envelope beyond perhaps where even most Republicans would be comfortable going.
Trump is doing on waterboarding and torture what he has done on other issues like immigration in this election: stretching conservative views to the extreme -- and seeing if they break or simply keep stretching.