Republican presidential candidate Donald Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE said on Sunday called politics "rough stuff," saying tactics used by his rivals are worse than the ones he faced in the real estate business.

"These people are worse than Manhattan real estate developers," he said on ABC's "This Week."

"This is rough stuff, politics."

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Trump said he was hit hard on Saturday in South Carolina by two robo calls supporting rival Ted Cruz Rafael (Ted) Edward CruzLoeffler calls for hearing in wake of Netflix's 'Cuties' Health care in the crosshairs with new Trump Supreme Court list 'Parks and Rec' cast members hosting special reunion to raise money for Wisconsin Democrats MORE that he called "tough and unfair."

"This is something I didn't anticipate," he said.

"So I said to myself, 'Wow, this is a tough business.'"

But Trump, who won by a large margin in the South Carolina Republican primary on Saturday, said he thought the calls and attack ads would have had a bigger effect on the outcome.

"I didn't know I was going to win by that much. And we won by a lot. You know, we won every congressional district, also we got every single delegate. So that was -- that was sort of record-setting stuff," he said.

"But they really hit me hard with negative ads."