Withering put-downs and sharp exchanges dominated the third Republican presidential debate as the one-time frontrunner Jeb Bush came off worst on a night when his protégé Marco Rubio shone.
Mr Rubio, the 44-year-old senator who climbed Florida’s political ladder under the watch of Mr Bush (62) as governor, scored the biggest point of the debate when an attack by his former mentor backfired.
In the heated TV debate, the brother and son of two former presidents challenged Mr Rubio on his voting record in the Senate and the time he spent there.
“What is it, like a French work week where you have three days to show up?” he asked, urging him to concede his seat to someone else.
Mr Rubio shot back, saying that Mr Bush never criticised Arizona senator John McCain for missing Senate votes when he ran for the White House in 2008.
“The only reason you’re doing it now is because we’re running for the same position and someone has convinced you that attacking me is going to help you,” the Cuban-American senator responded.
The two Floridians slugged it out on a stage of 11 candidates as the Republican battle for the White House grows even more bitter, with candidates attempting to knock out their closest rivals.
Outsiders, businessman Donald Trump and retired neurosurgeon Ben Carson, lead the polls but they were subdued as the lower-ranking contenders commanded the debate that focused on economic matters.
Mr Rubio and Mr Bush, who are battling it out for the party's moderate establishment core, are polling third and fourth respectively behind them, trailed closely by Texas senator Ted Cruz, the conservative firebrand, and former corporate executive Carly Fiorina.
Mr Cruz, another winner on the night, took advantage of a clumsily-moderated debate and aggressive questioning, scolding the CNBC hosts for starting fights rather than encouraging serious debate.
"The questions that have been asked so far in this debate illustrate why the American people don't trust the media," the Texan said to the loudest applause and hoots of the night from the audience in Colorado.
He said: "This is not a cage match. And if you look at the questions: Donald Trump, are you a comic book villain? Ben Carson, can you do math? John Kasich, will you insult two people over here? Marco Rubio, why don't you resign? Jeb Bush, why have your numbers fallen?"
The Democratic candidates in their first debate earlier this month received soft questions, said Mr Cruz, comparing that party’s candidates to “the Bolsheviks versus the Mensheviks”.
Blistering rebuke
CNBC, one of the debate's big losers, drew a blistering rebuke from Reince Priebus, chairman of the Republican National Committee, the debate's organiser, who accused the hosts of asking "gotcha" questions.
“The performance by the CNBC moderators was extremely disappointing and did a disservice to their network, our candidates and voters,” he said.
Mr Trump, property tycoon and reality TV star, lost his lead to Mr Carson in a CBS/New York Times poll this week and was leapfrogged by the African-American conservative in Iowa, the first state in the country to nominate the party's candidates in 95 days' time.
He saved his most stinging attack of the third debate for Ohio governor John Kasich, who is ninth in the polls.
Mr Kasich, another contender fighting for the support of the party’s establishment, targeted the two frontrunners, arguing that Dr Carson and Mr Trump were not fit to serve as president.
“My great concern is that we’re on the verge of picking someone who cannot do this job,” he said.
Mr Trump responded by attacking him on Ohio's economic gains from the energy boom, his past work for Wall Street firm Lehman Brothers, whose collapse triggered the financial crisis, and his low poll numbers.
“John got lucky with a thing called fracking,” he said. “Lehman Brothers started it all, and he was a managing partner… Then his poll numbers tanked. That’s why he’s on the end [of the stage].”
Mr Bush came off worse on the night. He was one of the most mentioned names on Twitter and the most searched Google, but clocked the lowest share of the debate time.
He suffered in another attack by the combative Chris Christie, the New Jersey governor who hijacked Mr Bush's rambling answer to a question on whether fantasy football amounted to gambling.
“We have $19 trillion in debt, we have people out of work, we have al-Qaeda and ISIS (Islamic State) attacking us and we’re talking about fantasy football? Can we stop?” said Mr Christie, who is running tenth in the polls, drawing a warm response from the Republican crowd.
Interrupted by a badgering CNBC moderator John Harwood while answering another question, the irascible Christie snapped: “Do you want me to answer or do you want to answer? Because I got to tell you the truth, even in New Jersey what you’re doing is called rude.”
The Republican candidates will have a chance to spar again at the next debate in Milwaukee, Wisconsin on November 10th.
