The Republican was the clear favourite when the 2016 campaign began
Jeb Bush has ended speculation about his chances of making it to the White House by suspending his campaign to run for president.
The Republican fared poorly in earlier contests in Iowa and New Hampshire and said the race had been "hard fought" but that voters of those three states had spoken.
The son of former President George HW Bush and brother to former President George W Bush, entered the 2016 campaign as the favourite, but was unable to convert a sizeable fundraising advantage into success at the polls.
It comes as Hillary Clinton won the Nevada Democratic caucuses, rebounding after a second-place finish to rival Bernie Sanders in New Hampshire.
The presidential hopeful won after beating back a stronger-than-expected challenge from Mr Sanders.
With 65% of the precincts reporting, Mrs Clinton was leading with 52.2% of the vote to Mr Sanders' 47.8%.
Meanwhile, Donald Trump won in South Carolina, a second-straight victory for the billionaire real estate mogul after his first-place finish in New Hampshire.
Senators Ted Cruz and Marco Rubio appeared to be in a close battle for second place in the Palmetto State, according to projections by Fox News and NBC News, which called the contest for Mr Trump.
Mr Bush earlier told Sky News he thought Mr Trump was a "bully", and the former Florida governor argued he was the one "to fix the mess" in an "insecure" world.
Mrs Clinton, who narrowly won in Iowa but was crushed by the Vermont Senator in New Hampshire, was counting on a major Hispanic voter turnout, especially among Las Vegas hotel and casino employees.
Declaring herself to be the natural Hispanic ally on immigration, she promised a quick path to citizenship for those in the country illegally if she was elected president.
"This is your win," Mrs Clinton said in a tweet, thanking supporters for her victory.
Mrs Clinton's narrow margin of victory in a state where she was once expected to win by double digits suggested the Democratic nominating race could be long and hard-fought, with Mr Sanders performing strongly in a state with a heavy minority population.