Bush left reeling as rookie Rubio bares his teeth
Marco Rubio, the Florida senator and presidential candidate, has attacked his political mentor Jeb Bush - the former governor of Florida - in a bruising battle during the Republican debate.
Mr Rubio was asked about his failure to attend sessions in the senate and rising concern in Florida that he was neglecting his constituents in favour of his presidential campaign.
A powerful local newspaper in Florida, the 'Sun Sentinel', published a strongly worded attack on the Cuban-American politician on Wednesday morning, telling him he should "resign, not rip us off".
He protested that he was still serving his constituents, but also working for a bigger cause.
"Marco, when you signed up for this, this was a six-year term and you should be showing up to work," said Mr Bush, who was a popular governor of the state from 1999 to 2007.
"I mean literally, the senate, what is it like, a French work week? You get, like, three days where you have to show up?"
Mr Rubio turned angrily on his former mentor.
"Someone has convinced you that attacking me is going to help you," said Mr Rubio, needling the 62-year-old veteran Republican for his falling poll ratings.
"My campaign is going to be about the future of America. I'm not running against Governor Bush. I'm not running against everyone else on this stage. I'm running for president."
Mr Rubio has presented himself as a fresh-faced solution to the Republican conundrum, versus the Washington elite embodied by Mr Bush, whose brother and father were both presidents.
Mr Bush, an early favourite, has failed to impress so far. On Friday, he was forced to cut his staff numbers by 40pc and is currently in fifth place, trailing Ben Carson and Donald Trump by a wide margin.
Susan McManus, a politics professor in Florida who knows both men, recently commented: "It was a shock to many, many people when Marco stood; the presumption was that Marco would never run against Jeb.
"They didn't have barbecues together but the mentor relationship was very strong.
"But Marco's history is one of taking risks. People are just starting to realise what we've realised in Florida for a while, that he's a superb debater, he's quick on his feet and he has depth of knowledge."
Mr Bush went into the debate needed a big performance, and the general consensus was that, if anything, he went backwards.
He needed a strong showing to silence the doubters. He did not get it.
A lacklustre showing is likely to spur even more questions about his viability as a top-tier candidate, according to political strategists and donors.
"If he was looking to revive his campaign and replenish his coffers, he did not do himself any justice," said Republican strategist Ford O'Connell.
Mr Bush's campaign manager insisted immediately after the debate that the former Florida governor would remain in the race for the long haul.
But Mr Bush came into the debate after dramatically downsizing his campaign staff and huddling with nervous donors to calm their fears, the result of persistent single-digit showings in opinion polls.
Those donors are probably even more jittery now as he seemed to come out on the losing end of exchanges with Mr Rubio and New Jersey Governor Chris Christie and disappeared from the screen for long stretches of time.
Mr Rubio was magnanimous in a sweep of TV interviews, telling CNN that he thought Bush had been a "great governor."
"I don't believe that the way I'm going to win is by going after him or anybody else," he said.
At one point, Mr Bush was asked whether fantasy football should be treated as gambling.
He joked about his own fantasy team before suggesting that the government should get more involved.
It was a rare moment when Bush got a chance to show his sense of humour and one that otherwise might have gone over well.
But Chris Christie pounced, to the approval of the audience: "Are we really talking about getting government involved in fantasy football? We have - wait a second - we have $19 trillion (€17.3 trillion) in debt. We have people out of work.
"We have Isil and al Qaeda attacking us. And we're talking about fantasy football?" (© Daily Telegraph, London)