Media playback is unsupported on your device Media caption Jeb Bush delivered an emotional concession speech after a disappointing run in the Republican presidential race

Former Florida governor Jeb Bush has dropped out of the Republican race for US president after failing to rank high in the first three state contests.

He came a distant fourth in Saturday's South Carolina vote, which was won by billionaire estate mogul Donald Trump.

"Today I am suspending my campaign," an emotional Mr Bush told his supporters.

Once a favourite mainstream candidate for the Republicans - and brother and son to two US presidents - Mr Bush saw his campaign flag in recent months.

The Bush who failed

In South Carolina, where he was pinning his hopes on a resurgence in his campaign, he came joint fourth with Ohio governor John Kasich.

"The people from Iowa, South Carolina and New Hampshire have spoken, and I really respect their decision," the former governor said, in reference to his poor performance in the three states that have already held their presidential primaries and caucuses.

"I've got an incredible life and for me, public service has been the highlight of this life," he added.

Media playback is unsupported on your device Media caption Marco Rubio celebrated second place as if it was a victory

Jeb Bush, the son of former President George HW Bush and brother to former President George W Bush, failed to translate huge funds and Republican donations into votes.

He was overtaken in the polls by Mr Trump and Texas Senator Ted Cruz, who sold themselves as anti-establishment alternatives to his mainstream candidacy.

The Republican pack will now look to back Florida Senator Marco Rubio, once Jeb Bush's protégé, who tied in second place with Mr Cruz in South Carolina.

"After tonight, this has become a three-person race and we will win the nomination," Mr Rubio told his supporters as the results emerged.

A look back at the doomed campaign

Media playback is unsupported on your device Media caption Here's a message mash up of how Hillary Clinton and Jeb Bush made their campaign announcements. (Video by David Botti)