The victories by Trump, who is running as an anti-establishment outsider, and Clinton, a preeminent political insider, solidified their positions as the front-runners to win their parties' respective nominations ahead of the Nov. 8 presidential election.

The night's most prominent casualty, Bush suffered a distant fourth place finish in the Republican contest and announced he had suspended his campaign, ending his dream of becoming a third Bush president after his father and brother.

"The people of Iowa, New Hampshire and South Carolina have spoken, and I really respect their decision," an emotional Bush said in Columbia. He finished far out of the running in each of the first three states.

By winning both South Carolina and New Hampshire and holding leads in 13 states that hold Republican contests on March 1, Trump was arguably on track to win the nomination, an outcome that seemed astounding to contemplate when he entered the race last summer.

"It's going to be very difficult for him to be derailed at this point," said Hogan Gidley, who was a senior adviser to former Republican candidate Mike Huckabee.   

The 69-year-old real estate billionaire and reality TV star was declared the winner in South Carolina about an hour after polls closed, and launched into a feisty victory speech.

"Let's put this thing away," Trump told cheering supporters in Spartanburg. He denounced TV pundits for saying there could be enough anti-Trump votes to beat him when the race thins further.

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