Even before it started it seemed as though Jeb Bush's campaign - which stumbled and lurched before it sputtered and died - had dragged on forever.

This was not an illusion. For all practical purposes his run started in 2012, though he did not announce he was "actively exploring" a run until December 2014.

A day shy of six months later he formally announced his candidacy. This was a matter of unedifying but legal tactics. By prolonging his exploration phase right up to the six-month limit, Bush skirted campaign finance regulations that would have kicked in the following day.

Bush had used his time well and by the end of 2015 he had milked his mega-donors of  $US100 million.

This war chest was totemic. It was meant not only to pay for the campaign but to ward off potential rivals with its sheer size, to permanently install Bush as the frontrunner.

According to the plan, he was to sail from victory to victory in the early contests. The rest of the field would slip away.

It didn't turn out that way.

A month after he announced his candidacy in June last year, Donald Trump overtook him in the polls. Bush was never to lead the race again, and by the time he was beaten in South Carolina he was coming sixth in national polls.

Trump, with all his bluster and bombast and his even bigger pile of loot, didn't just wrong foot the Bush campaign, he mercilessly tormented the candidate as a "low energy" loser.

In Iowa Bush was humiliated. Ted Cruz won the state with 27.6 percent. Trump secured 24.4 percent. Bush won 2.8 percent.

On to New Hampshire, a state his key supporters said he had to win. In the shaky days before the poll Bush dragged his poor old mum, the popular former first lady Barbara Bush out on the stump. Trump sniggered that he was hiding behind her skirts.

During one town hall meeting Bush sought to differentiate himself from Trump, making a pitch for himself as stable and quiet achiever.

He finished his spiel and the crowd remained utterly silent. "Please clap," he said sadly. They did, politely.

Trump won, with 35 percent, Bush came fourth with 11 percent.

It was in the lead-up to the South Carolina race that it really turned ugly. No Bush had ever lost in South Carolina, and the family political network in the state is deep and old.

Bush was in so much trouble that he trotted out his older brother George W. Bush, who had stayed out of politics since his presidency ended in the shame and blood of Iraq.

Trump attacked the Bush family root and branch. In a bitter debate, he accused George W. Bush of lying about the existence of weapons of mass destruction in Iraq as a pretext for the disastrous war.

In a later interview he retreated – a little – over the allegation that Bush lied, but expanded on his view that the invasion was a disaster. In fact he called it the worst decision made by an American president, ever.

South Carolina, not only a Bush state but a state steeped in military tradition, home to some of the nation's largest military bases, responded by carrying Trump to another thumping victory. He won around 33 per cent of the vote. Marco Rubio and Cruz practically tied for second place at around 22 per cent. Bush barely managed to crack eight per cent.

Finally Bush conceded that after spending over four years of his own life and well over $100 million of other people's money, having achieved nothing but further tarnishing his family's already questionable political legacy, his race was over.

"The people of Iowa, New Hampshire, and South Carolina have spoken," Bush said, struggling with emotion during a speech in South Carolina's capital, Columbia. "And I really respect their decision. So tonight, I am suspending my campaign."