Donald Trump. REUTERS/Jonathan Ernst WASHINGTON (Reuters) - Republican presidential candidate Donald Trump, who has for months rained withering ridicule on onetime party favorite Jeb Bush, on Sunday refused to take responsibility for the former Florida governor's exit from the 2016 White House race.

"I just don't know what did him in," Trump, who won South Carolina's Republican primary election handily on Saturday, said in an interview on CNN.

Trump had repeatedly made Bush the target of pointed attacks throughout his campaign for the Republican nomination to run in the Nov. 8 general election, labeling him "weak," "low-energy" and "an embarrassment" to the Bush political dynasty.

On Sunday, Trump denied any role he may have played in taking down Bush, who ended his campaign on Saturday night after a fourth-place finish in South Carolina.

"Jeb fought very hard," the billionaire businessman said. "It wasn't his time. That's all."

Bush, the brother of one president and the son of another, had prided himself as the only candidate to attack Trump head-on throughout the campaign and frequently accused him of lacking ideas.

Republican presidential candidates, businessman Donald Trump, left, and former Florida Gov. Jeb Bush talk together before the start of the CNN Republican presidential debate at the Ronald Reagan Presidential Library and Museum on Wednesday, Sept. 16, 2015, in Simi Valley, Calif. AP Photo/Chris Carlson He appeared to take one last jab at Trump in his concession speech on Saturday, saying: "Despite what you may have heard, ideas matter. Policy matters."

Sounding less like his normally combative self, Trump on Sunday credited Bush in a pair of interviews with having fought hard in the campaign and called him "very capable."

"Those last couple of weeks he was on television so much, I was looking, I'd say, 'Man, I've never seen anything like this,'" Trump said on CNN.

He did, however, chide Bush for having run "brutal" negative ads against him, saying he was "a little bit offended."

"So, you know, this is a tough business, I will tell you," the billionaire real-estate mogul said of presidential politics.

"I think real estate in Manhattan is a lot easier."