Jeb Bush's bid to follow his brother and father to the White House ended Saturday after another miserable performance, this time in the South Carolina primary where he not only distantly trailed the Republican front-runner Donald Trump but was also decisively beaten by fellow Floridian, Senator Marco Rubio.

Mr. Bush's defeat was expected. The faltering campaign of the once-presumed favourite of the party's establishment had burned through more than $150-million and "Jeb," who for months avoided using his family name, had fumbled at every turn.

He couldn't decide whether he backed his brother's 2003 war in Iraq, failed to win the key endorsement of South Carolina Governor Nikki Haley, was out-jabbed by Mr. Trump in debates and on social media and outmanoeuvred by the younger, more charismatic Mr. Rubio. When, in desperation, Jeb turned to his brother and mother last week to campaign for him, it was too late.

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In quitting, Mr. Bush, 63, a former Florida governor, ended what once seemed possible – that the two modern American political dynasties, the Clintons and the Bushes, would vie again for the presidency.

On his way out, Mr. Bush took a final jab at Mr. Trump, suggesting the bombastic billionaire who has defied the political pundits and his rivals by tapping into a vast pool of citizen fury at the political elites and politics as usual in Washington was insufficiently humble and honest to be president.

"I have had a front-row seat to this office for much of my adult life," Mr. Bush said, his voice cracking with emotion. "I have seen fallible men rise up to the challenges of our time, with humility and clarity of purpose … to make our nation safer, stronger and freer. I firmly believe the American people must entrust this office to someone who understands that whoever holds it is the servant, not the master, someone who will commit to that service with honour and decency."

The someone Mr. Bush had in mind clearly wasn't the New York property magnate who lampooned him mercilessly as weak, low-energy and bumbling.

In victory, Mr. Trump was – at least momentarily – magnanimous about Mr. Bush.

"He's a good person, he's a good man," Mr. Trump said. "It was really just not his time. You know, four years ago, I think he would have won,"

Mr. Trump predicted he would win the Republican nomination and face Hillary Clinton, the former first lady and Democratic front-runner, in November's presidential election.

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"Frankly, if she gets indicted, that's the only way she's going to be stopped [in winning her party's nomination]," Mr. Trump said of the ongoing investigation into Ms. Clinton's use of a private e-mail server while she was secretary of state.

With Mr. Bush gone, Mr. Rubio emerges as the mostly likely Republican mainstream alternative to Mr. Trump.