Republican Jeb Bush has ended his campaign for the US presidency after a disappointing finish in South Carolina.

The former Florida governor and political scion told supporters that he’d tried to stay true to what he believes.

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Still, he was lagging far behind in the primary in South Carolina, where his well-organised campaign was outmatched by insurgent billionaire Donald Trump, and Senators Ted Cruz and Marco Rubio.

“I’m proud of the campaign that we’ve run to unify our country and to advocate conservative solutions,” a visibly emotional Bush said.

“The presidency is bigger than any one person. It’s certainly bigger than any one candidate.

Bush hadn’t expected such a strong showing from Trump. Getty

“I firmly believe the American people must entrust this office to someone who understands that whoever holds it is a servant not the master,” Bush said.

The son of George HW Bush and brother of George W Bush entered the race to huge expectations in June, and quickly fuelled them with fundraising.

Bush and his allies raised more than $US150 million ($A210 million) by the end of 2015 – far more than any of his Republican rivals.

However, Bush’s presence in the race and fundraising potential wasn’t enough to dissuade more than a dozen other Republicans from entering the race, including fellow Floridian, Senator Marco Rubio.

Bush’s failure to ignite was not simply a factor of the size of the Republican field.

Bush, like others, was caught off-guard by the durable popularity of political outsiders – particularly Trump.

Bush took shots at Trump’s lack of experience while Trump attacked Bush’s family legacy, particularly the unpopular Iraq war waged by his brother George W Bush.

Bush went on to finish sixth in the Iowa caucuses, but barely squeezed ahead of Rubio in New Hampshire for a fourth place finish.

South Carolina was viewed as a last early voting state for Bush to make a mark.

Having previously kept his family at arm’s length, Bush brought all family ties to the forefront ahead of South Carolina.

His father and brother both won the South Carolina primary when they were seeking the presidency, and he had set his hopes high there for a campaign revival