The former Florida governor's attempt to revive his White House hopes during Wednesday's Republican debate by taking on his former protege, Sen. Marco Rubio , backfired badly.

Instead, he delivered a performance drained of passion, fire and inspiration followed by a testy post-game interview that added up to a disastrous night for Bush.

Bush was already struggling going into the debate -- grappling with low poll numbers and a weak base in early voting states.

But his performance only confirmed and deepened damning perceptions of his political skills and questions about his stomach for the fight. And Bush is already trying to stave off the stench of decay that quickly gathers around losing campaigns.

"The end is not near -- life is good," he told reporters in New Hampshire on Thursday.

But when a candidate is forced to make such a statement, and when the political classes begin to ask questions about how long a campaign can stay in the race, it's never good news.

"I think his campaign is on life support," said Ford O' Connell, a Republican political consultant not currently affiliated with a 2016 presidential candidate.

Photos: Jeb Bush's life Former Florida Gov. Jeb Bush waves as he takes the stage as he formally announces he is joining the race for president with a speech June 15, 2015, at Miami Dade College in Miami. Hide Caption 1 of 21 Photos: Jeb Bush's life Former Florida governor Jeb Bush shakes hands with attendees after speaking at the 42nd annual Conservative Political Action Conference on February 27 in National Harbor, Maryland. Hide Caption 2 of 21 Photos: Jeb Bush's life Bush takes a selfie with a guest at a luncheon hosted by the Chicago Council on Global Affairs on February 18 in Chicago. Bush delivered his first major foreign policy speech at the event. Hide Caption 3 of 21 Photos: Jeb Bush's life Bush hands out items for Holiday Food Baskets to those in need outside the Little Havana offices of CAMACOL, the Latin American Chamber of Commerce on December 17 in Miami. Hide Caption 4 of 21 Photos: Jeb Bush's life Bush waves to the audience at the Tampa Bay Times Forum in Tampa, Florida, on August 30, 2012, on the final day of the Republican National Convention. Hide Caption 5 of 21 Photos: Jeb Bush's life Bush (left) and wife Columba Bush attend the 2012 Lincoln Center Institute Gala at Frederick P. Rose Hall, Jazz at Lincoln Center on March 7, 2012, in New York City. Hide Caption 6 of 21 Photos: Jeb Bush's life President Barack Obama (left) speaks about Bush (center) while visiting Miami Central Senior High School on March 4, 2011 in Miami, Florida. The visit focused on education. Hide Caption 7 of 21 Photos: Jeb Bush's life Bush (left) speaks with Brazilian President in charge Jose Alancar during a meeting at Planalto Palace in Brasilia, April 17, 2007. Bush was in Brazil to speak about sugar and ethanol business. Hide Caption 8 of 21 Photos: Jeb Bush's life Then-Texas Governor Rick Perry (center) testifies as Bush (right) and then-Arizona Governor Janet Napolitano (left) listen during a hearing before the House Committee on Homeland Security on Capitol Hill October 19, 2005. Hide Caption 9 of 21 Photos: Jeb Bush's life Bush gives a thumbs up signal from his car as he leaves a local polling station after casting his vote in Coral Gables, Florida, November 5, 2002. Hide Caption 10 of 21 Photos: Jeb Bush's life Bush walks out of the West Wing after meeting with his brother, then-President George W. Bush, at the White House January 9, 2002. Governor Bush participated in the signing ceremony of the Everglades Protection Agreement. Hide Caption 11 of 21 Photos: Jeb Bush's life Then-Mexican President Vincente Fox (left) and Bush hold a press conference September 7, 2001, in Miami. Fox visited Florida to attend the Americas Conference and deliver a speech to speak about issues such as immigration. Hide Caption 12 of 21 Photos: Jeb Bush's life Then-President George W. Bush (right) is greeted by Jeb Bush on March 21, 2001, at Orlando International Airport in Orlando, Florida. President Bush was in Orlando to attend the American College of Cardiology Annual Convention. Hide Caption 13 of 21 Photos: Jeb Bush's life Bush speaks during a press conference at the Carandolet Government Palace in Quito, January 18, 2006. Bush and a businessmen delegation were in a two-day visit to talk about a free trade agreement. Hide Caption 14 of 21 Photos: Jeb Bush's life Bush speaks to reporters after meeting with the Florida State Cabinet at the Florida State Capitol Building November 16, 2000, in Tallahassee, Florida. Hide Caption 15 of 21 Photos: Jeb Bush's life Then-President George W. Bush (left) and Jeb Bush (right), raise their arms onstage following a rally at the Florida State Fairgrounds, October 25, 2000, in Brandon, Florida. Hide Caption 16 of 21 Photos: Jeb Bush's life Jeb Bush (left) and then-President George W. Bush stand with their arms around each other's shoulders at a rally in Miami, Florida, September 22, 2000. Hide Caption 17 of 21 Photos: Jeb Bush's life Then-President George W. Bush (right) and Jeb Bush go through the line for strawberries during a stop at the Stawberry Festival March 12, 2000 in Plant City, Florida. Hide Caption 18 of 21 Photos: Jeb Bush's life The Bush family, (left to right) former U.S. President George W., former Florida Governor Jeb, former President George H.W. and his wife Barbara, watch play during the Foursomes matches September 25, 1999 at The Country Club in Brookline, Massachusetts the site of the 33rd Ryder Cup Matches. Hide Caption 19 of 21 Photos: Jeb Bush's life Former President George H.W. Bush (second left), his wife Barbara Bush (left), their son Jeb Bush (center), then-first lady Hillary Clinton (second right), and former then-President Bill Clinton (right) look up to see the U.S. Army Golden Knights parachute team November 6, 1997 at the conclusion of the dedication ceremony of the George Bush Library in College Station, Texas. Hide Caption 20 of 21 Photos: Jeb Bush's life Portrait of the Bush family in front of their Kennebunkport, Maine house August 24, 1986. Pictured, back row: Margaret holding daughter Marshall, Marvin Bush, Bill LeBlond. Pictured, front row: Neil Bush holding son Pierce, Sharon, George W. Bush holding daughter Barbara, Laura Bush holding daughter Jenna, Barbara Bush, George Bush, Sam LeBlond, Doro Bush Lebond, George P. (Jeb's son), Jeb Bush holding son Jebby, Columba Bush and Noelle Bush. Hide Caption 21 of 21

Former Minnesota Gov. Tim Pawlenty, a Republican who unsuccessfully ran for the White House in 2012, said that Bush had "underperformed" all along, and now needed a quick fix.

"He is going to have to up his game or the market place is going to move away from him," Pawlenty said on CNN.

David Axelrod, a former Democratic political guru who is now a CNN analyst, said that Bush endured a "terrible night."

"I think it put him in a really dangerous position," said Axelrod.

Bush's trip to New Hampshire was planned to build on hoped-for momentum after the debate in Boulder, Colorado, and to launch the kind of revivalist mojo that John McCain conjured up in the 2008 campaign.

Instead, the trip is being overshadowed by a media post mortem not just of Bush's debate performance but his entire campaign.

"It is not on life support, we have the most money, we have the greatest organization. We're going to be fine," Bush said in Portsmouth, New Hampshire.

Bush also held a meet-and-greet with supporters and appeared alongside a banner reading "Jeb Can Fix It" which was meant to refer to his vow to get Washington working again, but in the light of Wednesday night appeared more like an ironic comment on the need to revive his campaign.

Photos: Republican debates in Colorado Photos: Republican debates in Colorado John Kasich, left, and Donald Trump argue across fellow candidates during the GOP debate at the University of Colorado in Boulder on Wednesday, October 28. Fourteen candidates participated in the third set of Republican presidential debates. Hide Caption 1 of 15 Photos: Republican debates in Colorado The debate was Ben Carson's first since rising to the top of the polls. He slammed "PC culture" and said the idea that a person who believes marriage is between a man and a woman is a homophobe was "one of the myths the left perpetrates on our society." Hide Caption 2 of 15 Photos: Republican debates in Colorado Ted Cruz got a big cheer from the crowd with an attack on the debate moderators. "How about talking about the substantive issues people care about?" he asked. The mainstream media was one of the night's big targets. Hide Caption 3 of 15 Photos: Republican debates in Colorado Jeb Bush went after Marco Rubio for missing votes in the Senate while running for the White House. "Just resign and let someone else take the job," Bush said. Rubio fired back, saying Bush never took issue with Sen. John McCain missing votes when he was running for president. "The only reason you're doing it now is because we're running for the same position." Hide Caption 4 of 15 Photos: Republican debates in Colorado Mike Huckabee likened the federal government to a NORAD blimp that became untethered earlier in the day. "If you saw that blimp that got cut loose in Maryland today, it's the perfect example of government." He said it ran away and then "got too big" to "get rid of." Hide Caption 5 of 15 Photos: Republican debates in Colorado In her closing statement, Carly Fiorina said, "I may not be your dream candidate just yet, but I can assure you I'm Hillary Clinton's worst nightmare." Hide Caption 6 of 15 Photos: Republican debates in Colorado John Kasich wasted no time in going on the attack. In response to a question to each candidate on what their greatest weakness is, Kasich immediately pivoted to slamming the front-runners, though not by name. "My great concern is that we are on the verge perhaps of picking someone who cannot do this job," he said. Hide Caption 7 of 15 Photos: Republican debates in Colorado Rand Paul, right, speaks as Chris Christie looks on. Paul said, "If you're not willing to gradually raise the age, you're not serious about" fixing Social Security and Medicare. On the same topic, Christie hit the Democrats for making big promises. "When they say they want to give it to you free, keep your hand on your wallet," he said. Hide Caption 8 of 15 Photos: Republican debates in Colorado Trump, who had predicted early that the debate would be unfair, criticized CNBC's moderators for asking "ridiculous questions." Hide Caption 9 of 15 Photos: Republican debates in Colorado From left, Bobby Jindal, Rick Santorum, George Pataki and Lindsey Graham take the stage for the second-tier GOP debate that took place before the main event at the University of Colorado. Hide Caption 10 of 15 Photos: Republican debates in Colorado Attendees listen to the first debate. For all four men, the pressure was on to raise their national poll numbers to qualify for the main debate stage in November. Hide Caption 11 of 15 Photos: Republican debates in Colorado Sen. Lindsey Graham, a national security hawk, called President Barack Obama an "incompetent commander in chief" and also took aim at the Democratic candidates. Regarding Bernie Sanders, Graham said: "The No. 2 guy went to the Soviet Union on his honeymoon, and I don't think he ever came back." Hide Caption 12 of 15 Photos: Republican debates in Colorado Former New York Gov. George Pataki, center, also went after the Democrats. He said Hillary Clinton's private email server as secretary of state "disqualifies" her from being president. Hide Caption 13 of 15 Photos: Republican debates in Colorado Louisiana Gov. Bobby Jindal accused Democrats of "trying to turn the American dream into a European nightmare." Hide Caption 14 of 15 Photos: Republican debates in Colorado "A true conservative wants to create a level playing field," former Pennsylvania Sen. Rick Santorum said. "That's what government is supposed to do. ... And when it comes to our manufacturers, the level playing field is not in the United States." Hide Caption 15 of 15

While Bush has the financial muscle, organization and support from a super PAC to stay in the race, sooner of later he must demonstrate genuine lift in his poll numbers, with first nominating votes to be cast in just three months.

The magnitude of Bush's challenge is rooted in fact that the deficiencies on display Wednesday night, and in evidence throughout his campaign, don't seem like they might be easily mendable.

They center on the candidate himself and the perceptions of failure now dogging a candidacy clearly suffering from overly high initial expectations. He must worry that donors who powered the fundraising machine at the center of his candidacy will also soon begin to doubt him -- or look for a more dynamic candidate elsewhere.

Thursday night, Bush held a conference call with donors, state campaign chairs and other key leaders. Two participants on the call said that Bush acknowledged that he could have done better at the debate, but said he was confident in his campaign's plan and strategy.

They described the mood as one of concern, not panic. One of the participants noted that many of Jeb's backers have been through other campaign cycles and aren't the "run-and-hide types."

But, the participant said, "that doesn't mean there aren't real concerns."

Then there is the question of how Bush can improve his technique in debates -- with the next Republican clash only two weeks away already shaping up as a test in which he will be under an even more unforgiving spotlight.

Speaking in New London, New Hampshire Thursday night, Bush was asked by a reporter what he was going to do to get better in debates.

"Look we've got eight more debates," he said, then added sarcastically, "We're going to have to do what other candidates do, which is rudely interrupt, not answer the questions that are asked and hopefully the debate moderators will actually ask more substantive questions as well. It's going fine."

He was then asked if he was having any fun, to which he responded: "Oh yeah, lots of fun."

Opening the door for others

Perhaps the most worrying consideration for Bush is that his performance has opened the door for others -- particularly Rubio, who got rave reviews after the debate and now threatens to usurp Bush as the top GOP establishment candidate.

"The establishment buzz around Rubio right now .... is going to help him continue that slow, steady climb into that poll position in the establishment lane," said Kevin Madden, a former top aide to Mitt Romney who is now a CNN analyst.

The clash between Rubio and Bush may turn out to be one of the most clarifying snapshots of the campaign -- because in that moment, the weaknesses of one man were exacerbated by the strengths of another.

In a clearly choreographed attack, Bush seized on complaints that in his desire to wage his presidential campaign, Rubio had neglected his real job and had let Floridians down with his poor voting record in the Senate.

But Rubio unleashed a furious counter-attack, in an almost Shakespearean tableau of a protege spurning his mentor, showing the ruthless guile, killer instinct and willingness to do anything in pursuit of victory that Bush appears to lack.

"The only reason you are 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," Rubio said.

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The riposte was so devastating because it jabbed Bush over the clearly obvious fact that he disdains hardball politics, is desperately trying to find a footing in the campaign and his heart was not really in the attack.

CNN analyst Ana Navarro, who knows both men well, said that the exchange made her teeth hurt. While arguing that Bush remained the best qualified person on the stage to be president, she admitted he needed to pull off a swift recovery.

"He has got to figure out a way how to slay and kill this debate boogie monster dead," she said.

A key Bush supporter in New Hampshire said on condition of anonymity that he believed that his candidate could still pull off a comeback, and said the debate format did little to help Bush or showcase his mastery of policy or problem solving skills.

"He will do what he has to do on site -- when he is visiting New Hampshire and stay connected to the people," the supporter said.

In a post-debate interview with CNN's Dana Bash, Bush implicitly admitted that he lacks the histrionics that help candidates prosper on debate stages and appeared frustrated, complaining that the CNBC moderators asked a question about fantasy football and not real issues that mattered.

"Nope, not frustrated," Bush told Bash, though his thin grin and demeanor appeared to indicate otherwise.

"I'm running for president of the United States. I'm running with heart. I'm not a performer. If they're looking for an entertainer-in-chief, I'm probably not the guy," he said.

Bush appears to ignore the fact that performance is fundamental to politics, according to some observers.

"Part of leadership is to inspire and in this media, news, political world, you have to be inspiring," said Pawlenty.

"He is going to have to up his game because the debate last night and even before, the response was that was not sufficiently inspiring."

And his statement to Bash that if voters are looking for a reform-oriented conservative with a proven record of results, he is the ideal candidate, pointed to a deeper problem for Bush. Simply put, in a year when outside candidates have captured the Zeitgeist voters simply are not yet buying what he is trying to sell.

Bush rejects that criticism: "They are buying it, right now in New Hampshire. More people are going to buy it as we campaign harder," Bush said Thursday.

But many observers believe Bush might be a victim of poor timing and that his problems could therefore be insurmountable.

"In a lot of other cycles, Jeb could have run and won, but given the sort of groundswell for political outsiders and the ghosts of his last name, it is just very tough," said O'Connell.

"No matter what he says, he either comes across as privileged or entitled -- he just doesn't seem to be able to overcome it."