Republican 2016 US presidential candidate businessman Donald Trump during the first official Republican presidential candidates debate in Cleveland. Thomson Reuters Donald Trump went back and forth with NBC host Chuck Todd on Sunday in one of his most combative interviews since announcing his presidential candidacy earlier this summer.

In a 37-minute conversation on "Meet The Press," Todd pushed Trump on a wide range of issues with which the real-estate magnate would presumably be confronted if he won the presidency in 2016. It forced Trump to be on the defensive on everything from his college record, to outsourcing, to the US role in NATO.

Todd focused specifically on the reality-television personality's past statements on immigration, challenging Trump's comments that Mexico was "killing" the US economy.

"How are they killing us?" Todd asked, speaking over Trump. "Their GDP is lower than ours. This is not a country that is killing us. Just by the stats."

Todd also pushed Trump on his claim that Hillary Clinton was the "worst secretary of state," asking Trump to name other secretaries of state. When Trump said that he didn't want to "name names," Todd appeared exasperated.

"Everything with you's the best or the worst," Todd said.

"No, it's not," Trump said.

"There's no nuance," Todd said, before Trump changed the focus back to Clinton.

Though the real-estate magnate laid out few concrete policy proposals, Sunday's interview showed the extent to which Trump is occasionally out of step with his rivals in the Republican field, which hasn't escaped the notice of his detractors.

Trump said that he "possibly" donated to Planned Parenthood and suggested he supports affirmative action, laws banning businesses from firing gay employees, and statehood for Washington, D.C.

He also elaborated on his skepticism of entering the US into military conflicts without receiving some money in return. And, after admitting that he watches political talk shows for foreign-policy advice, he questioned whether the US should spend money defending South Korea and admitted that he doesn't "care that much" if Ukraine joins NATO.

"I'm a fan of fairness. I'm a fan of common sense. I'm certainly not a fan of us being against Russia ... for Ukraine when Germany is sitting back, you know, accepting all the oil and gas that they can get from Russia," Trump said.

"So why isn't Germany involved? You know, she's a great leader. And one of the reasons that [German Chancellor Angela] Merkel's a great leader is she sort of says, 'Oh, good, let the United States handle it.'"

Republican presidential candidate Donald Trump addresses a GOP fundraising event, August 11, 2015, in Birch Run, Michigan. AP

Referencing an interview that Trump gave in 1990 t0 Playboy magazine, Todd asked the real-estate magnate if his candidacy had made Americans "all part of a reality show."

"Look, my life has been an interesting life. I’ve had a lot of fun. I’m leading in the polls. I go on your show — you will get the highest ratings you’ve had in years," Trump said.

Trump has made dozens of television appearances since announcing his candidacy, but few have been as lengthy or in-depth as Sunday's Meet The Press interview. Some observers were quick to point out that the format exposed how thin some of Trump's positions were on substance.

As he continues to dominate in the polls, Trump has started to take a more calculated approach to tough political situations. He has dialed down his rhetoric and attempted to emphasize his record of supporting women in the business world after controversy surrounding his feud with Fox News host Megyn Kelly.

Trump is also beginning to elaborate on his policy positions — on Sunday, he released his first official policy paper, which outlines his plan to curb illegal immigration.

But the real-estate mogul isn't likely to stray too far from his famous rhetorical style.

Asked on Saturday about when he would release his immigration policy proposal, Trump pointed out that the press was far more interested in it than voters.

"I know the press wants it," Trump said, according to The Washington Post. "I don't think the people care. I think they trust me. I think they know I'm going to make good deals for them."