Republican presidential candidate Donald TrumpDonald TrumpDem rep: Trump can't deliver on promise because of Russia probe Trump turns up heat on AG Sessions over recusal Trump: 'I won't say' that I should be on Mount Rushmore 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."

Trump said he was hit hard on Saturday in South Carolina by two robo calls supporting rival Ted CruzTed CruzMcCain votes to advance ObamaCare repeal, replace after vowing to oppose Senate rejects ObamaCare repeal, replacement amendment Senate Dem: We’re trying to block a recess appointment to replace Sessions 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."