Senior Republican figures rallied behind the embattled New Jersey governor, Chris Christie, on Sunday, in a coordinated effort to rescue the tattered reputation of a man who until this this week many considered the party’s best hope for regaining the White House in 2016.

Reince Priebus, the chairman of the Republican National Committee, led the charge, insisting that “Americans are a forgiving people” who will respect the contrition Christie has displayed in the wake of the scandal over unnecessary lane closures on the George Washington bridge.

“Everyone is fallible,” Priebus said. “We all make mistakes. But the real question is: 'What do you do when mistakes happen?'"

Other top Republicans who leapt to Christie’s defence were the former New York mayor Rudy Giuliani and John McCain, the Arizona senator and 2008 presidential candidate.

Christie fired a senior official from his office after claiming she had lied to him about her role in the September lane closures, which caused widespread traffic chaos and appear to have been part of a vendetta against political adversaries.

In a 115-minute press conference on Thursday, Christie said he had been “embarrassed and humiliated” by the conduct of people on his team, but claimed to have had no knowledge of the alleged conspiracy. The scandal has thrown into doubt Christie’s suitability for the presidency, raising questions about what critics allege is a domineering, even bullying style.

"There is no question: he admitted mistakes happen, he admitted he trusted people that lied to him," Priebus, whose committee oversees the process to elect a Republican presidential nominee, said on NBC’s Meet the Press. “Americans are a forgiving people. But they are forgiving when you take ownership, you admit mistakes, you take corrective action – that is what Chris Christie showed.”

Giuliani, a friend of Christie, said the governor had been “in campaign mode” around the time of the bridge closures and should not be held accountable for actions by his staff.

“He says he didn’t realise. He says he didn’t know,” Giuliani told ABC’s This Week. “I think it is pretty darn credible. He wouldn’t make this blanket denial unless it is not true.” Of the controversy, he added: “I think this does just go away.”

But elsewhere on Sunday there was little sign of the scandal fading.

Christie was considered a frontrunner amid a field of Republican presidential hopefuls who have so far failed to inspire the party's base or make much impact in the wider public, and Democrats are keen to capitalise on his perceived weaknesses.

Questions remain about whether Christie really was completely unaware of the lane-closure plan hatched by some of his closest aides and, if so, why they did not feel obliged to inform their boss. On Friday, a new tranche of documents was released, revealing that senior officials connected to Christie’s office were warned on the first day of the lane closures that they were impeding police and emergency workers, but pressed on with the move, which was disguised as a traffic test, for another three days.

The lawmaker heading the state assembly investigation into the bridge controversy, John Wisniewski, told CBS's Face the Nation he did not think it was credible for Christie’s chief of staff, deputy chief staff, communications director and chief counsel to have all been in email communication over the lane closures and “how to spin [them] to the press”, without Christie's knowledge.

The fact Christie was in the midst of a re-election campaign made it all the more likely four top officials would have wanted to inform him of an email from the executive director of the Port Authority, who said the lane closures were unlawful, Wisniewski said.

“It just strains credibility that they didn’t look at those documents and say: ‘We ought to let him know about it,'" Wisniewski said.

Thomas Kean, a former New Jersey governor who remains a senior figure in the Republican Party, dealt another blow to Christie when he told the Washington Post that Christie may have created a culture in which his aides “will never say no to him, and that is dangerous”.

Kean, a mentor to Christie, whom he has known since the governor was a teenager, described Christie as “the most able politician since Bill Clinton” but then added: “On the other hand, you look at these other qualities and ask: ‘Do you really want that in your president?’”

McCain’s support also came with caveats. While he said Christie had done “an excellent job” answering questions at Thursday’s marathon press conference, McCain conceded that any further revelations might prove problematic. “I think he can now move on as long as another shoe doesn’t drop,” the Arizona senator told CNN. “Too often, we have seen these things that it’s not the end of the story.”

He added: “Having gone through this, I know that you’ve got to answer every question. You can’t leave any question unanswered."

McCain, Giuliani and Priebus all tried to deflect criticism of Christie by drawing attention to controversies that plagued the Obama administration in 2013, including mixed messages from the administration over the September 2012 attack on the US consulate in Benghazi, Libya, and criticisms of the Internal Revenue Service over its alleged targeting of political groups.

The similarity of language used by the three Republicans grandees suggested they were adhering to a script of talking points designed to support Christie after the worst week in his political career.

One senior Republican offered comparably muted support for Christie. Widely perceived as a presidential contender for 2016, the Florida senator Marco Rubio is one of the few people in the party who might benefit from the demise of New Jersey's charismatic governor.

“I think it would be a mistake for me and people like me to comment on this,” Rubio said on CBS. “First of all, we don’t know all the facts. I think this is a story that is still developing and we should reserve judgment.”