Bush entered the 2016 US presidential race as the early front-runner, but he struggled to gain traction with voters amid the current appetite for outsiders such as Donald Trump and Ted Cruz.

"Tonight I am suspending my campaign," an emotional Bush said after finishing a disappointing fourth in South Carolina's primary.

"I truly hope that these ideas that we have laid out will serve as a blueprint for a generation of conservative leaders at every level of government so that we can take back our country," the 62-year-old said.

Jeb Bush is the son of former President George H.W. Bush, and brother of former president George W. Bush. Having initially kept his family at arm's length, Bush brought his family connections to the forefront as he campaigned to win South Carolina.

But voters this election cycle appeared wary of sending another member of the Bush family to the White House. His popularity nosedived against more outspoken Republican rivals like businessman Donald Trump and Texas Senator Ted Cruz.

In Iowa caucuses on February 1, he finished a disappointing sixth place, followed by foruth in New Hampshire a week later.

Bush was also dealt a blow on Wednesday as he failed to gain the endorsement of South Carolina governor Nikki Haley, who instead endorsed Florida Senator Marco Rubio.

Trump, who won the South Carolina primary on Saturday night, made no mention of Bush's decision during a speech, despite hammering his rival throughout the campaign.

bw/blc (AP, AFP)